Some Windows 10 preloads have a small EFI System Partition of 100MB which is enough for 10 but might cause the upgrade to Windows 11 to fail with the message ‘We couldn’t update system reserved partition’ error code 0xc1900104, or error code 0x800f0922.
Without the need for partition resizing tools you should be able to work around this issue by following these steps:
- Search for cmd. Press-and-hold or right-click on Command Prompt in the results, and select Run as administrator.
- At the command prompt, type mountvol y: /s and then hit Enter. This will add the Y: drive letter to access the System Partition.
- Switch to the Y drive by typing Y: and press Enter. Then, navigate to the Fonts folder by typing cd EFI\Microsoft\Boot\Fonts. Once there, type del *.ttf to delete font files. The system may ask you if you are sure to continue, press Y and then Enter to continue.
now retry the upgrade