On 12th December 2013, Microsoft released Windows RT 8.1, Windows 8.1, and Windows Server 2012 R2 update rollup: December 2013 – KB2903939 which will be offered to most folk via Windows Update.
There are reports that this update is failing with neither the Windows Update troubleshooter or the alternative DISM.exe /online /cleanup-image /restore health e.t.c. (that the troubleshooter suggests as an alternate approach) fixing the problem.
All the usual caveats apply – so don’t sue me … but if you are similarly affected, try this:
1. Download KB2903939 as a standalone from here: http://www.microsoft.com/en-us/download/details.aspx?id=41294 (if you have a 32bit – X86 install, you need this instead)
2. Actually download BOTH the subsequently offered Windows8.1-KB2903939-x64.msu AND Windows8.1-KB2911134-x64.msu
3. Run Windows8.1-KB2911134-x64.msu – (but NOT Windows8.1-KB2903939-x64.msu)
4. Spin up Powershell (type “Powershell” in an admin DOS cmd prompt).
5. In the Powershell prompt, run each of these commands:
set-service trustedinstaller -startuptype Disabled
reg load HKLM\COMPONENTS $env:windir\system32\config\COMPONENTS
Remove-Item -Path HKLM:\Components\DerivedData\VersionedIndex\* -Recurse
reg unload HKLM\COMPONENTS
set-service trustedinstaller -startuptype Automatic
6. Run Windows8.1-KB2903939-x64.msu (that you downloaded in step 2)
7. Restart – when prompted.