0x800f0922 — update fails, System Reserved partition full or no route to Microsoft

The Secure Boot or a cumulative update fails. This deletes files from a system partition — read every step before starting.

1. Check how much free space the partition actually has.

   PowerShellCopy

   Get-Partition | Where-Object { $_.Type -eq 'System' -or $_.IsSystem } | Get-Volume | Format-Table DriveLetter, FileSystemLabel, @{n='FreeMB';e={[int]($_.SizeRemaining/1MB)}}, @{n='SizeMB';e={[int]($_.Size/1MB)}}

   The update needs roughly 15 MB free here. Anything under about 40 MB will fail, and the error says nothing about disk space.

2. Give the partition a temporary drive letter so you can see inside it.

   PowerShellCopy

   $p = Get-Partition | Where-Object { $_.IsSystem -and -not $_.DriveLetter } | Select-Object -First 1Set-Partition -InputObject $p -NewDriveLetter Y

3. On a BIOS/MBR machine, the space is nearly always old language folders under Y:\Boot. Delete everything except en-GB and en-US.

   PowerShellCopy

   Get-ChildItem Y:\Boot -Directory | Where-Object Name -notin 'en-GB','en-US','Fonts','Resources' | Select-Object Name

   Look at the list before deleting anything. These are boot-time localisation files; removing the one your firmware uses leaves a machine that boots to a blank screen.

4. Remove them once you have read the list.

   PowerShellCopy

   Get-ChildItem Y:\Boot -Directory | Where-Object Name -notin 'en-GB','en-US','Fonts','Resources' | Remove-Item -Recurse -Force

5. On a UEFI machine the partition is the EFI System Partition instead. Clear the font cache there, which is usually the bulk of it.

   PowerShellCopy

   Remove-Item 'Y:\EFI\Microsoft\Boot\Fonts\*' -Force -ErrorAction SilentlyContinue

6. Remove the temporary drive letter again — leaving it assigned exposes the boot partition in Explorer.

   PowerShellCopy

   Remove-PartitionAccessPath -InputObject $p -AccessPath 'Y:\'

7. Retry the update.

Get-Volume | Where-Object FileSystemLabel -eq 'System Reserved' | Format-Table @{n='FreeMB';e={[int]($_.SizeRemaining/1MB)}}

A VPN or proxy is present, or a .NET update is the one failing.

1. Disconnect any VPN client completely, not just the tunnel — some leave a route in place.

   The update transaction has to reach Microsoft's servers to validate; a split-tunnel that captures those routes fails it with this code.

2. Check the WinHTTP proxy, which is what the update service uses rather than the browser's setting.

   Command PromptCopy

   netsh winhttp show proxy

3. Clear it if it should not be there.

   Command PromptCopy

   netsh winhttp reset proxy

4. For a .NET failure, repair the installed version with Microsoft's .NET Repair Tool before retrying.

5. Reset the update cache and retry.

   PowerShellCopy

   Stop-Service wuauserv, bits -ForceRename-Item C:\Windows\SoftwareDistribution SoftwareDistribution.oldStart-Service bits, wuauserv

Get-WinEvent -LogName 'Setup' -MaxEvents 20 | Format-Table TimeCreated, Id, Message -AutoSize