A problem on your computer is preventing updates from being downloaded or installed

A problem on your computer is preventing updates from being downloaded or installed.

Depois de instalar o SP3 do Windows XP, pode não mais fazer atualizações do Windows Update e não instalar as atualizações vá no prompt do DOS e registre as DLL.

REGSVR32 WUAPI.DLL
REGSVR32 WUAUENG1.DLL
REGSVR32 ATL.DLL
REGSVR32 WUPS2.DLL
REGSVR32 WUCLTUI.DLL
REGSVR32 WUPS.DLL
REGSVR32 WUWEB.DLL
REGSVR32 WUAUENG.DLL

Dica tirada do site abaixo:

http://www.technipages.com/error-a-problem-on-your-computer-is-preventing-updates-from-being-downloaded.html#comment-1917