I've found the followin procedure in another website and it worked for me:
(1)
Go to Start / All Programs / Accessories. Right Click the 'Command Prompt' item and click the 'Run As Administrator' option.
In the Command Prompt window, Paste the following command.
REGSVR32 %SYSTEMROOT%\SYSTEM32\WUAUENG.DLL
Press ENTER.
You should see a popup that says the command succeeded.
Exit the command prompt and try Windows Update again.
(2)
1. Click Start. Choose Run.
2. In the Run box, type: regsvr32.exe wuaueng.dll
3. Click OK.
original link:
"WindowsUpdate_80070424" "WindowsUpdate_dt000" - TechNet Forums