Updated on Sep. 22, 2026
Position: Resource - Disk Utilities - No EFI System Partition Was Found: Causes and How to Fix It?
You are installing Windows, or maybe trying to set up Ubuntu alongside it, and everything stops. A message pops up: "No EFI System Partition was found." You might have also seen it while running a boot repair tool. Either way, you are stuck, and if you are not sure what an EFI System Partition even is, the error does not give you much to go on.
This error means the system is trying to boot in UEFI mode but cannot find the EFI System Partition (ESP) it needs. That sounds bad, but it usually is not. The ESP is a small partition that holds boot files. If it is missing, damaged, or simply not being looked for on the right disk, you will see this message. The fix depends on what caused it, and in most situations you can resolve it without reinstalling Windows or losing any files.
This article covers what the EFI System Partition is, all the common causes of this error, how to diagnose the problem on your specific disk, and seven different ways to fix it. There is also a section for Ubuntu users who see this message during installation, a comparison of the small partitions that people often confuse with each other, and a list of mistakes worth avoiding.
Table of Contents:
Most people who see the "No EFI System Partition was found" error have never heard of this partition before. That is normal. Windows does a good job hiding it. There is no drive letter, no label, and you would never know it exists unless you go looking for it with a disk tool.
So what is it? The EFI System Partition, or ESP, is where your computer stores the files it needs to start Windows when the system uses UEFI firmware. Without it, the UEFI firmware does not know how to hand off control to Windows. Think of it as the "launch instructions" that sit on the disk, waiting for the firmware to read them every time you press the power button.
Those instructions include Windows Boot Manager (the file is called bootmgfw.efi), the UEFI boot files that the firmware expects to find, and the BCD store, which is essentially a configuration file that points to your Windows installation. If you have a dual-boot setup with Linux, the ESP may also hold GRUB or other boot files for that system.
The reason this partition matters so much is that UEFI and Legacy BIOS boot in fundamentally different ways. A UEFI system reads the ESP, loads Windows Boot Manager, which reads the BCD, which loads winload.efi, which loads Windows. A Legacy BIOS system does not look for an ESP at all. It reads the first sector of the disk (the MBR), jumps to the active partition, runs bootmgr, and goes from there. Two completely different paths from power button to desktop.
When the "No EFI System Partition was found" error appears, it means the firmware tried to follow the UEFI path but could not find the ESP to start the chain.
| Property | EFI System Partition |
| Partition style | GPT |
| File system | FAT32 |
| Typical size | 100 to 500 MB (varies) |
| Drive letter | Usually none (hidden by default) |
| Purpose | Stores UEFI boot files |
| User data | Not intended for personal files |
One detail worth knowing: Microsoft's documentation specifies a minimum ESP size of 200 MB for drives with 512-byte or 512e sectors, and 300 MB for 4Kn drives. Older Windows versions sometimes created 100 MB ESPs, and some OEM systems ship with 500 MB ones. The size varies depending on how Windows was installed, so do not rely on size alone to figure out whether a partition is an ESP.
1. Windows Is Still Running
If you discover through Disk Management or DiskGenius that the ESP is gone but Windows is running, do not assume everything is fine. The firmware might have a cached boot entry that is keeping the system alive. That cache can be cleared by a BIOS update or a firmware reset, at which point the computer will not boot.
A missing ESP can also cause problems with automatic repair, boot recovery tools, and disk cloning operations. Fix it now while the system is still working, rather than waiting for it to fail at the worst possible moment.
2. The Computer Cannot Boot
You might see "Windows Boot Manager" missing from the BIOS boot options, "Operating System not found," or the system might enter a boot loop.
A missing ESP does not mean your Windows installation or your files are gone. The boot configuration and the operating system are separate things. In the vast majority of cases, the Windows partition is completely intact and the boot environment just needs to be rebuilt. Try repairing the boot configuration before resorting to a full reinstall.
There is no single answer to this. The error can be triggered by half a dozen different problems, and the right fix depends on which one you are dealing with. The sections below cover every common cause.
1. The EFI System Partition Was Deleted
Sometimes the ESP is just gone. It might have happened during a Windows reinstall when you deleted all partitions and started fresh. Or you were resizing partitions and removed one that turned out to be the ESP. Maybe you cloned a disk but the cloning tool skipped the ESP because it looked like an unimportant sliver of unallocated space. Any of these will leave you with a GPT disk that has no ESP, and the next time something tries to boot in UEFI mode, you get the error.
2. The EFI Partition Exists but Is Damaged
This is a different situation from a missing ESP, and people sometimes conflate the two. The partition is still physically there on the disk. A partition tool will show it. But something inside is broken. The FAT32 file system might be corrupted. The boot files might be incomplete or garbled. The BCD store might have been damaged by a failed Windows update or a sudden power loss during a write operation. Bad sectors on the disk can also chew up parts of the ESP.
The reason the distinction matters is that the repair approach is different. For a missing ESP, you need to create one. For a damaged ESP, you usually need to repair the files inside it, or in some cases reformat the EFI partition to FAT32 and rewrite the boot files without touching the partition structure itself.
Read more: How to Delete EFI System Partition in Windows 11/10? [Full Guide]
3. Windows Was Installed in Legacy BIOS Mode
This one catches a lot of people off guard. Legacy BIOS uses MBR partition tables and boots through the Master Boot Record. UEFI uses GPT partition tables and boots through the ESP. If Windows was installed in Legacy mode, the disk has no ESP because it was never needed. If you then boot a tool or installer in UEFI mode, that tool looks for an ESP that does not exist. You get the error, but nothing is actually wrong with Windows. The problem is just a mode mismatch.
4. The Installation USB Booted in the Wrong Mode
This is the most common cause during dual-boot setups with Linux. Windows was installed in Legacy mode on an MBR disk. You plug in a bootable Ubuntu USB and start the installer. The USB boots in UEFI mode (which is the default on most modern boards), the installer scans for an ESP, finds nothing, and throws the error.
Do not immediately create an EFI partition when you see this. First check how Windows was installed, then match the boot mode. Creating an ESP on an MBR disk that is running in Legacy mode will not solve the real problem.
5. The EFI Partition Is on a Different Drive
This is the one that really surprises people. You have one SSD with Windows on it. Everything seems fine. Then one day you remove a secondary HDD that you were not using for anything important, and suddenly Windows will not boot. Turns out, when you installed Windows with both drives connected, the installer put the ESP on Disk 1 instead of Disk 0. Your Windows partition is on Disk 0. The boot files are on Disk 1. Remove Disk 1 and the whole boot chain breaks.
If you only have one drive in your system, this is not your problem. But if you have two or more internal drives, this is worth checking early on.
6. The EFI Partition Is Not Recognized Correctly
Less common, but it happens. The ESP is on the disk, formatted as FAT32, and it even has the right files in it. But the partition type identifier is wrong. Maybe a cloning tool copied the partition data but did not set the correct type GUID. Or the partition table got partially corrupted. The result is that the firmware and Windows both look at this partition and do not recognize it as an ESP, even though it looks like one.
One related mistake that comes up a lot: people try to find the ESP by looking for a partition with a drive letter. ESPs do not have drive letters by default. Windows hides them on purpose. You need to look at the partition type and file system, not the drive letter.
Before you start creating partitions or running repair commands, spend two minutes checking what your disk actually looks like. I have seen people create a second ESP on a disk that already had one, or worse, format the wrong partition, because they skipped this step.
The fastest way to get a rough idea. Press Win + X, pick Disk Management, and look at the disk where Windows is installed. You are looking for a small partition, usually somewhere between 100 and 500 MB, with no drive letter and no label. If the disk is GPT and you see something like this, it is probably the ESP. If you do not see anything matching that description, the ESP may be missing. Or it could be on a different disk entirely.
One limitation: Disk Management does not show partition type GUIDs. So you cannot be 100% certain that a small FAT32 partition is actually an ESP. It might be, but Disk Management will not confirm it for you.
More detail, but you need to use the command line. Open Command Prompt as Administrator:
diskpart
list disk
list volume
From list disk, check the GPT column. An asterisk there means GPT, no asterisk means MBR. From list volume, look for a small FAT32 volume with no letter. That is your likely ESP candidate. Also note which disk number the Windows partition and the suspected ESP are on. If they are on different disks, that is relevant information and might explain the error entirely.
DiskGenius shows every partition on every physical disk in a single view, with partition type labels (EFI System, MSR, Recovery, and so on), file systems, and sizes. No guessing. You can see at a glance whether an ESP exists, which disk it lives on, and whether the system has correctly tagged it as an ESP. For multi-disk setups, this is the most convenient option because everything is laid out visually.
Maybe the boot mode in BIOS is wrong. This is the easiest thing to check and it costs nothing, so start here.
Restart the machine and get into BIOS setup. The key depends on the manufacturer. Del, F2, F12, and Esc are the most common ones. Once you are in, look for a setting called Boot Mode, Boot Configuration, or CSM (Compatibility Support Module). You want to see whether it is set to UEFI, Legacy, or something in between.
UEFI is what you need for GPT disks with an ESP. Legacy or CSM is what you need for MBR disks that do not have one. If the current setting does not match how Windows was installed, change it, save, and reboot. Problem solved.
But here is where people get burned: if Windows was installed in Legacy mode on an MBR disk, switching the BIOS to UEFI will not magically make it boot. It will fail. You need to actually convert the disk from MBR to GPT first (Fix 5 covers that). Changing the BIOS mode alone is only the right fix when the mode was changed by accident or by a firmware update.
At this point you need to know what kind of partition table your disk has, because that determines which of the remaining fixes apply to you. If you already checked in the diagnosis step above, you can skip ahead. If not, here is how to find out.
With DiskPart, run list disk and look at the GPT column. With Disk Management, right-click the disk number on the left. If "Convert to GPT Disk" is grayed out, the disk is already GPT. With DiskGenius Free Editon, the partition table type is shown directly in the disk info.
Once you know, here is what it means:
Your disk is GPT, BIOS is UEFI, and the ESP is present: the partition itself is probably fine. Your boot files might be corrupted. Go to Fix 3.
Your disk is GPT, BIOS is UEFI, but there is no ESP: you need to create one. Go to Fix 4.
Your disk is MBR and BIOS is UEFI: that is the mismatch. Either convert the disk to GPT (Fix 5) or switch BIOS back to Legacy.
Your disk is MBR and BIOS is Legacy: this is actually normal. MBR disks do not have ESPs. If you are seeing the "No EFI System Partition was found" error, it is coming from a tool that booted in UEFI mode, not from your actual system. Boot that tool in Legacy mode instead.
Your disk is GPT and BIOS is Legacy: unusual, and depends on what your firmware supports. Consider switching to UEFI.
If you end up needing to convert MBR to GPT, both Fix 5 (MBR2GPT) and Fix 7 (DiskGenius) can do it. Fix 7 handles the conversion, ESP creation, and boot file setup in a single pass.
our ESP is there, it is FAT32, it looks fine, but Windows still will not boot. The boot files inside the ESP are probably damaged or missing. BCDBoot can fix this. It is a Windows command-line tool that writes fresh boot files to the ESP.
You will need a GPT disk with an existing ESP, a working Windows partition (the files are there, just the boot config is broken), and access to a command prompt through either WinRE or WinPE.
Boot from a Windows USB or WinPE drive and open Command Prompt. Shift+F10 gets you there during Windows Setup.
Now, this next part is where things go wrong for a lot of people. In the recovery environment, your Windows partition is probably not on C:. It could be D:, E:, or something else depending on how many partitions and drives are present. You have to check before running bcdboot, because if you guess wrong, the command either fails or creates boot files pointing at nothing useful.
diskpart
list volume
exit
Look through the volumes. Find the one that has your Windows installation. It will be NTFS and roughly the size you expect. Note its letter. Then find the small FAT32 volume with no letter. That is the ESP. Assign it a letter:
diskpart
select volume X
assign letter=S
exit
Replace X with the volume number of the ESP.
Now run bcdboot:
bcdboot D:\Windows /s S: /f UEFI /l en-us
Swap in the real drive letters for your system. If you see "Boot files successfully created," you are done. Restart, pull out the USB, and see if Windows boots.
The disk is GPT but there is no ESP. You need to create one and then write boot files to it.
You need at least 200 MB of unallocated space on the system disk. If there is none, you will have to shrink an existing partition first.
A few warnings before you start:
Method A: Using DiskPart
Boot from Windows installation media or WinPE and open Command Prompt.
diskpart
list disk
select disk 0
list partition
select partition 2
shrink desired=300
create partition efi size=260
format fs=fat32 quick
assign letter=S
exit
Adjust the partition numbers as needed. Then write boot files: bcdboot C:\Windows /s S: /f UEFI /l en-us
Verify drive letters first (same process as Fix 3). Then restart, enter BIOS, and confirm the boot mode is set to UEFI.
Method B: Using DiskGenius Free Edition
For anyone who finds the command line uncomfortable, or who wants to see the partition layout before committing to any changes, DiskGenius does the same job through a point-and-click interface.
1. Open DiskGenius Free Edition.
2. Look at the system disk and find the unallocated space. If there is not any, right-click the Windows partition, select "Resize Partition," and drag the edge to free up around 300 MB.
3. Right-click the unallocated space and choose "Create ESP/MSR Partition".
4. Select "Create ESP partition", type 300 for the size, and click "OK".
5. Click "Save All". The program will ask whether to format the new partition. Click "Yes". It gets formatted as FAT32 automatically.
DiskPart and DiskGenius both create the same kind of partition. The end result is identical. The difference is really just how you interact with the tool. DiskPart is text-based and already on your machine. DiskGenius shows you a visual map of the disk so you can see exactly where the new ESP sits relative to the other partitions. When you are dealing with multiple disks and a bunch of partitions you do not recognize, that visual context can be the difference between confidence and guesswork.
Windows is running in Legacy mode on an MBR disk and you want to switch to UEFI/GPT without reinstalling.
MBR2GPT is a built-in Windows tool (Windows 10 version 1703 and later) that converts a disk from MBR to GPT. According to Microsoft's documentation, it validates the disk, creates an EFI System Partition, installs UEFI boot files, converts the partition table, and updates the BCD. All in one pass.
Good candidates for MBR2GPT: your disk is MBR but your hardware supports UEFI, you want to enable Secure Boot, you are preparing for a Windows 11 upgrade (which requires UEFI + GPT), or you have a working Windows environment to run it from.
Not a good fit: you are not sure about the current disk layout (diagnose first), you have no backup of your data, the disk has severe partition table issues, or you just need to fix boot files without converting the partition table.
Open Command Prompt as Administrator. Validate first (this checks everything without making changes): mbr2gpt /validate /disk:0 /allowFullOS
If validation passes: mbr2gpt /convert /disk:0 /allowFullOS
The tool handles the rest: shrinking the Windows partition if needed, creating the ESP, installing UEFI boot files, converting to GPT, and updating BCD.
After it finishes, go into BIOS and change the Boot Mode to UEFI. Then restart.
Read More:
If you prefer not to use the command line, DiskGenius Free can do the same conversion:
1. Launch DiskGenius Free Edition, right-click the MBR disk and choose "Convert To GUID Partition Table".
Tip: If your computer is not bootable for the moment, you can create a bootable USB drive using DiskGenius Free Edition.
2. Click "Save All" to save changes to the partition table.
The ESP was restored or recreated, maybe after recovering deleted partitions, and the boot environment needs to be set up from scratch.
How is this different from Fix 3? Fix 3 repairs boot files on an ESP that the system already knows about. Fix 6 is for situations where the ESP was gone, has been brought back, and now needs the full boot environment rebuilt, including the firmware boot entry.
Steps:
Boot into WinPE. Open Command Prompt. Identify partitions:
diskpart
list volume
select volume X
assign letter=S
exit
Rebuild: bcdboot D:\Windows /s S: /f UEFI /l en-us
If the BCD store is badly damaged, you may also need: bootrec /rebuildbcd
This scans for Windows installations and adds them to the BCD.
Check BIOS afterward to confirm the boot entry appears under Boot Options. Then restart.
Multiple things are wrong at once, or you would rather handle everything in one place with a graphical tool.
The previous fixes each tackle one problem: create an EFI partition, convert the table there, repair boot files somewhere else. Real-world boot failures often involve a combination. The disk is MBR, the ESP is missing, and the boot files are gone. Running through five separate command-line tools one at a time gets tedious and is easy to mess up.
DiskGenius has a Windows Boot Repair and Conversion feature under the "Tools" menu that brings all of these operations into a single workflow. It can:
Since your current Windows won't boot, you need to boot your computer from a WinPE USB drive. You can use DiskGenius Free Edition to create the bootable USB disk, or copy DiskGenius to a bootable USB drive created by other tools.
Once your computer boots from the USB drive, launch DiskGenius, and then try follow steps to repair boot issues:
1. In DiskGenius, go to "Tools" → "Windows Boot Repair and Conversion".
2. Configure settings for the system disk. Then click "Execute".
A lot of people who search for this error are not running Windows Setup. They are installing Ubuntu, either as a standalone system or alongside Windows. The Ask Ubuntu forums have many threads with this exact message as the title.
The cause is almost always a boot mode mismatch.
The Ubuntu installer checks the target disk for an ESP. If it boots in UEFI mode (which is the default on most boards made in the last decade) and finds no ESP, it reports the error. Usually this means Windows was installed in Legacy mode on an MBR disk, and there was never an ESP to begin with.
Boot into Windows. Press Win + R, type msinfo32, press Enter. Look for BIOS Mode in the System Summary.
• UEFI means Windows is running in UEFI mode. The disk should be GPT and have an ESP.
• Legacy means Windows is running in Legacy BIOS mode. The disk is MBR and has no ESP.
This tells you how to proceed.
If Windows is Legacy: Boot the Ubuntu USB in Legacy mode too. When you open the boot menu (usually F12 or Esc at startup), you will typically see two entries for the USB drive, one with "UEFI" in the name and one without. Pick the one without.
If Windows is UEFI: The Ubuntu installer should boot in UEFI mode, which is normally the default. If it still complains about a missing ESP, the partition may be on a different disk, or it may be encrypted by BitLocker. Use the "Something else" option during Ubuntu installation to manually inspect the partitions, find the existing FAT32 ESP, and set its mount point to /boot/efi. Do not format it.
Formatting the Wrong Partition
In DiskPart, selecting the wrong volume number is easy, especially with multiple disks attached. Formatting the Windows partition instead of the new ESP will destroy your operating system. Always run list volume and list partition before any destructive command, and double-check the sizes and file systems.
Deleting the MSR Partition
The MSR is 16 MB, has no file system, and has no drive letter. It looks useless. It is not. Deleting it can cause problems with Windows Update, BitLocker, and future partition operations. Leave it.
Creating an ESP on an MBR Disk
If the disk is MBR, creating a FAT32 partition and trying to use it as an ESP generally will not work. UEFI firmware expects the ESP on a GPT disk. Convert to GPT first (Fix 5), then create the ESP (Fix 4).
Assuming Windows Is on C:\
In WinRE and WinPE, drive letters change. Your Windows partition might be D:, E:, or something else. Running bcdboot C:\Windows when Windows is actually on D: will fail. Check with list volume every single time.
Running diskpart clean Without a Backup
diskpart clean erases all partition information from a disk. clean all writes zeros to every sector. These commands have legitimate uses, but running them on a disk with data you want to keep, without a backup, is asking for trouble.
Reinstalling Windows Too Quickly
This is the mistake that costs the most. A boot error does not mean Windows is broken. The data and the boot configuration are different things. Before wiping and reinstalling, ask yourself: is the Windows partition still there with all my files? If so, repair the boot environment instead (Fix 3 through Fix 6). If the Windows partition itself was accidentally formatted, try recovering it first with a tool like DiskGenius before resorting to a clean install. Only if the entire disk has been wiped does a reinstall become the practical choice.
Changing BIOS Mode Blindly
Switching from Legacy to UEFI or the reverse without knowing how Windows was installed is a reliable way to make a computer unbootable. Check first with msinfo32 or by looking at the partition table type.
Can Windows boot without an EFI System Partition?
In UEFI mode, no. The ESP is required. In Legacy BIOS mode, yes, because Legacy booting uses the MBR and does not need an ESP at all. If your system is set to Legacy and your disk is MBR, having no ESP is normal.
How do I know if my EFI partition is missing?
Use DiskPart: diskpart, list disk (check for GPT), list volume (look for a small FAT32 partition). If the disk is GPT but has no FAT32 partition in the 100 to 500 MB range, the ESP is probably missing. DiskGenius gives you the same information in a visual layout.
Can I create an EFI partition without reinstalling Windows?
Yes. Fix 4 covers two methods (DiskPart and DiskGenius). Both create the ESP on the existing disk without touching the Windows installation, then you use bcdboot to add boot files. Takes a few minutes.
What is the difference between EFI and MSR partitions?
The ESP uses FAT32 and stores UEFI boot files. The MSR has no file system and no boot files. It is used internally by Windows for GPT management. Both are small and have no drive letter, which is why people mix them up. The comparison table earlier in this article has more detail.
Can DiskGenius create or repair an EFI partition?
Yes. There are two options: Create ESP/MSR Partition (Fix 4B), which creates an ESP in unallocated space through a graphical interface, and Windows Boot Repair and Conversion (Fix 7), which can create an ESP, repair boot files, convert MBR to GPT or the reverse, and switch between UEFI and Legacy boot modes. Both are available in the free edition of DiskGenius.
How to Avoid EFI Partition Problems in the Future?
DiskGenius is a one-stop solution to recover lost data, manage partitions, and back up data in Windows.
Download
Facebook
YouTube
X