Error 0xc1420121 when installing a Feature Update

When you attempt to install a feature update, the error 0xc1420121 may appear.

The setupact.log may show the following entries:

Info                  SP     Mounting WIM file C:\$WINDOWS.~BT\Sources\SafeOS\winre.wim to C:\$WINDOWS.~BT\Sources\SafeOS\SafeOS.Mount
Info                  SP     WIM index 1
Info                  SP     Working directory C:\$WINDOWS.~BT\Work
Warning               SP     Failed to get WimMount ImagePath, 0x80070002
[12592] OpenFilterPort:(408)
[12592] FltCommVerifyFilterPresent:(502)
[12592] WIMMountImageHandle:(1090)
[12592] StateStoreRemoveMountedImage:(1124)
[12592] WIMMountImageHandle:(1332)
Error                 SP     CMountWIM::DoExecute: Failed to mount WIM file C:\$WINDOWS.~BT\Sources\SafeOS\winre.wim. Error 0xC1420121[gle=0xc1420121]
Error                 SP     Operation failed: Mount WIM file C:\$WINDOWS.~BT\Sources\SafeOS\winre.wim, index 1 to C:\$WINDOWS.~BT\Sources\SafeOS\SafeOS.Mount. Error: 0xC1420121[gle=0x000000b7]
Info                  MOUPG  PreFinalize: Registering Setup Platform error: [0xC1420121]
Error                 SP     ExecuteOperations: Failed execution phase Pre-Finalize. Error: 0xC1420121

Cause

The error 0xc1420121 occurs if the wimmount.sys driver or its registration is missing from the system. This prevents WIM files from being mounted and thus causes the error during the setup.

• Error Code  : 0xc1420121
• Description : The image could not be mounted because the wimmount.sys driver is not installed on this machine. To fix this error, install the wimmount.sys driver.

Running these commands from admin Command Prompt should show the status of the wimmount driver/service:

sc.exe qc WimMount & sc.exe query WimMount

dir C:\windows\system32\drivers\wimmount.sys

net start wimmount

If you get the error “The specified service does not exist as an installed service“, that explains the problem.

Resolution

To fix the Windows setup error 0xc1420121, restore the missing wimmount service registration.

• Download wimmount.reg (zipped), unzip, and run it. Click Yes to confirm.
• Restart Windows. Note that shutting down the unit and powering it on will NOT help. You’ll need to **restart** Windows.

This restores the wimmount entry in the following registry key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WIMMount

INFO: Contents of wimmount.reg

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WIMMount]
"DebugFlags"=dword:00000000
"Description"="@%SystemRoot%\\system32\\drivers\\wimmount.sys,-102"
"DisplayName"="@%SystemRoot%\\system32\\drivers\\wimmount.sys,-101"
"ErrorControl"=dword:00000001
"Group"="FSFilter Infrastructure"
"ImagePath"=hex(2):73,00,79,00,73,00,74,00,65,00,6d,00,33,00,32,00,5c,00,64,00,\
  72,00,69,00,76,00,65,00,72,00,73,00,5c,00,77,00,69,00,6d,00,6d,00,6f,00,75,\
  00,6e,00,74,00,2e,00,73,00,79,00,73,00,00,00
"Start"=dword:00000003
"SupportedFeatures"=dword:00000003
"Tag"=dword:00000001
"Type"=dword:00000002

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WIMMount\Instances]
"DefaultInstance"="WIMMount"

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\WIMMount\Instances\WIMMount]
"Altitude"="180700"
"Flags"=dword:00000000

Additionally, ensure that the file “C:\windows\system32\drivers\wimmount.sys” exists on the computer.

That should resolve the error 0xc1420121.