how to install window 11 25h2 with 100mb efi

Question

have been trying to install windows 11 25h2 but it downloads upto 8percent it gives a response that could not update the system reserved partion

Answer 1

Hello, thank you for reaching out to Microsoft Q&A.

This error may occur if the System Reserved partition is full. You can free up approximately 13 MB of disk space by deleting unused font files (*.ttf) from the System Reserved partition.

Before deleting the files, you may have to find out if the Disk is GPT or MBR and then follow the prompts to delete the font files from your system reserved partition and install the updates.

Click the article below to see the complete steps and command lines to delete files from the partition. This link is safe as it was written by a trusted Microsoft MVP. Be cautious of any ads.

https://www.winhelponline.com/blog/we-couldnt-u...

Let me know if you still need more help.

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Answer 2

The error about not being able to update the System Reserved/EFI partition when installing Windows 11 25H2 is caused by insufficient free space on that partition. A 100 MB EFI/System Reserved partition is often too small for current Windows 11 feature updates.

For Windows 11, version 25H2 there is a specific known issue where updates fail with error 0x800f0922 when the EFI System Partition (ESP) has very little free space. The same underlying cause applies in this case: the update cannot write required boot files to the ESP.

Use these steps to work around it:

1. Free space or resize the EFI/System Reserved partition
   • The error text “could not update the system reserved partition” and error 0x800F0922 are associated with not enough free space in the System Reserved/EFI partition.
   • The long‑term fix is to increase the size of that partition (for example, using third‑party partitioning software) so that Windows Setup has enough room to update boot files. Microsoft documentation notes that 0x800F0922 “could also mean there isn't enough free space in the System Reserved partition” and suggests using third‑party software to increase its size.
2. If already on Windows 11 25H2 base build and only the May 2026 security update is failing
   • For devices already running Windows 11, version 25H2 where the May 2026 security update fails with 0x800f0922 due to low ESP space, there is a registry‑based workaround:
     1. Open Command Prompt as Administrator.
     2. Run:

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

     3. Restart the device.
     4. Retry installing the update.
   • This mitigates the specific May 2026 security update failure on devices with very small ESPs.
3. Retry the upgrade after fixing the partition
   • After resizing/freeing space on the System Reserved/EFI partition (and applying the registry workaround if applicable), run Windows Update or the Windows 11 setup again and let the installation continue.

If resizing partitions or editing the registry, ensure backups are created first, as incorrect changes can cause boot or system issues.

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References:

• Get help with Windows upgrade and installation errors
• Windows 11, version 25H2 known issues and notifications
• Resolved issues in Windows 11, version 25H2