Have you faced a problem where you’ve downloaded the Microsoft Updates file(s) but unable to install them? It kept saying “Unable to install blablabla”. I know this must be very annoying especially after recovering from a virus attack. Here I will show you one of the best solution that I’ve found and have solved LOTS of similar error. It is to re-register all your Windows Update DLL files (do it in command prompt):

regsvr32.exe %system%\wuweb.dll
regsvr32.exe %system%\wups2.dll
regsvr32.exe %system%\wups.dll
regsvr32.exe %system%\wucltui.dll
regsvr32.exe %system%\wuaueng1.dll
regsvr32.exe %system%\wuaueng.dll
regsvr32.exe %system%\wuapi.dll

*** If you are using XP/Vista, your %system% would be C:\Windows\System32. If you are using 2000/NT based system, your %system% would be C:\WinNT\System32. (considering that your OS is installed under C Drive)

Then restart your Automatic Update service under Administration Tools or restart your computer.

Walla, it’s done! :)