Cannot install Windows 11 25H2

Question

Cannot install Windows 11 25H2

Robert ONeill 60

Error message: We couldn't update the system reserved partition

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2 answers

Your answer

Answer 1

Ramesh 182K Volunteer Moderator

Hi Robert,

The error "We couldn't update the system reserved partition" occurs if the EFI partition is full.

Open Command Prompt (admin) and run these commands:

cmd.exe

reg add "HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc" /v EspPaddingPercent /t REG_DWORD /d 0 /f

mountvol Y: /s

del  /q  Y:\EFI\Microsoft\Boot\Fonts\*.ttf

powershell -command "GCI Y:\  -File -Recurse | Sort Length -descending | Select FullName, Length, Mode -first 10"

dir Y:\

Post the output here.

Robert ONeill 60 Reputation points

2026-10-01T17:48:58.2733333+00:00
Microsoft Windows [Version 10.0.26100.9457]

(c) Microsoft Corporation. All rights reserved.

C:\Windows\System32>reg add "HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc" /v EspPaddingPercent /t REG_DWORD /d 0 /f

The operation completed successfully.

C:\Windows\System32>mountvol Y: /s

C:\Windows\System32>del /q Y:\EFI\Microsoft\Boot\Fonts*.ttf

C:\Windows\System32>powershell -command "GCI Y:\ -File -Recurse | Sort Length -descending | Select FullName, Length, Mode -first 10"

FullName Length Mode

Y:\EFI\HP\DEVFW\Firmware.BIN 33180367 -a----

Y:\EFI\HP\SystemDiags\SysDiags.efi 13973520 -a----

Y:\EFI\HP\DEVFW\MeCurrent.BIN 11104544 -a----

Y:\EFI\Microsoft\Boot\bootmgfw.efi 3087200 -a----

Y:\EFI\Boot\bootx64.efi 3087200 -a----

Y:\EFI\Microsoft\Boot\bootmgfw.efi.{834bd253-2bfb-48c5-9acb-e65cbd5451ef} 3087200 ------

Y:\EFI\Microsoft\Boot\bootmgr.efi 3070456 -a----

Y:\EFI\Microsoft\Boot\memtest.efi 2610656 -a----

Y:\EFI\HP\DEVFW\Camera.bin 2466992 -a----

Y:\EFI\HP\BiosUpdate\BiosMgmt.efi 1480208 -a----

C:\Windows\System32>dir Y:\

Volume in drive Y has no label.

Volume Serial Number is 82EB-84A6

Directory of Y:\

10/01/2026 10:36 AM <DIR> EFI

0 File(s) 0 bytes 1 Dir(s) 11,175,936 bytes free

C:\Windows\System32>
Robert ONeill 60 Reputation points

2026-10-01T18:01:19.9933333+00:00

If I use Setting-Update it says 25H2 is not installed.

I run through the installation process, and it states that 25H2 is installed

I check properties of Laptop, and it shows 25h2 is installed

Run the Setting-Update to search for new updates, It tells me I need to install 25h2 again

I tried using the ISO image to install 25H2 and I get the error We couldn't update the system reserved partition" occurs if the EFI partition is full
Robert ONeill 60 Reputation points

2026-10-01T18:03:44.92+00:00
Here is output from running the code you recommended

Microsoft Windows [Version 10.0.26100.9457]

(c) Microsoft Corporation. All rights reserved.

C:\Windows\System32>reg add "HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc" /v EspPaddingPercent /t REG_DWORD /d 0 /f

The operation completed successfully.

C:\Windows\System32>mountvol Y: /s

C:\Windows\System32>del /q Y:\EFI\Microsoft\Boot\Fonts*.ttf

C:\Windows\System32>powershell -command "GCI Y:\ -File -Recurse | Sort Length -descending | Select FullName, Length, Mode -first 10"

FullName Length Mode

Y:\EFI\HP\DEVFW\Firmware.BIN 33180367 -a----

Y:\EFI\HP\SystemDiags\SysDiags.efi 13973520 -a----

Y:\EFI\HP\DEVFW\MeCurrent.BIN 11104544 -a----

Y:\EFI\Microsoft\Boot\bootmgfw.efi 3087200 -a----

Y:\EFI\Boot\bootx64.efi 3087200 -a----

Y:\EFI\Microsoft\Boot\bootmgfw.efi.{834bd253-2bfb-48c5-9acb-e65cbd5451ef} 3087200 ------

Y:\EFI\Microsoft\Boot\bootmgr.efi 3070456 -a----

Y:\EFI\Microsoft\Boot\memtest.efi 2610656 -a----

Y:\EFI\HP\DEVFW\Camera.bin 2466992 -a----

Y:\EFI\HP\BiosUpdate\BiosMgmt.efi 1480208 -a----

C:\Windows\System32>dir Y:\

Volume in drive Y has no label.

Volume Serial Number is 82EB-84A6

Directory of Y:\

10/01/2026 10:36 AM <DIR> EFI

0 File(s) 0 bytes 1 Dir(s) 11,175,936 bytes free

C:\Windows\System32>

Answer 2

This usually means Windows Update cannot write to the System Reserved partition or EFI System Partition because there is not enough free space there.

For Windows 11 25H2, start with these steps:

Install the latest available update first.
A known Windows 11, version 25H2 issue where updates failed with 0x800f0922 because of low free space on the EFI System Partition was resolved in updates released May 26, 2026 (KB5089573) and later.
If the device is still on an update released before that date and the install keeps failing, use the documented workaround below.
Workaround: set the ESP padding registry value to allow the update to install.
Warning: Editing the registry incorrectly can cause system issues. Back up the registry first.
- Open Command Prompt as Administrator.
- Run:
```
     reg add "HKLM\SYSTEM\CurrentControlSet\Control\Bfsvc" /v EspPaddingPercent /t REG_DWORD /d 0 /f
```
- Restart the PC.
- Try Windows Update again.
If the device is a consumer or non-managed PC, restart once or twice and retry.
Microsoft states this issue is also mitigated through Known Issue Rollback (KIR), and the fix propagates automatically to consumer and non-managed business devices.
Also check the common causes for 0x800f0922:
- Disconnect any VPN before retrying Windows Update.
- The error can also indicate insufficient free space in the System Reserved partition.
Before retrying the upgrade, apply the standard upgrade fixes:
- Unplug nonessential external hardware.
- Install all important Windows updates.
- Temporarily uninstall non-Microsoft antivirus software.
- Uninstall nonessential older software.

If the failure message remains generic, check the exact code in Start > Settings > Windows Update > Update history and use that code for the next troubleshooting step.