Microsoft's Knowledgebase article about it is below. Follow their suggestions.:
http://support.microsoft.com/kb/943144
And if that doesn't get it done, then try this:
Re-register all the Windows Update DLLs with the commands below
Click Start, click Run, type cmd, and then click OK.
Type the following commands. Press ENTER after each command.
regsvr32 wuapi.dll
regsvr32 wuaueng.dll
regsvr32 wuaueng1.dll
regsvr32 wucltui.dll
regsvr32 wups.dll
regsvr32 wups2.dll
regsvr32 wuweb.dll
Attempt to run Windows Update
Hope this helps.
Grif
I have restored my old Acer netbook to its original factory settings. It has a version with SP3 installed.
After the reinstallation, I click start/window update and then on Microsoft's site, I click "Express" and then I get the message "Checking for the latest updates for your computer" but nothing downloads.
Anyone has a suggestion?

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