Windows XP Service Pack 3 can break the automatic updates under certain circumstances due to a DLL that may not be registered. If the update system starts to fail with messages like “updates not installed”, do the following:

1. Stop the update service: net stop wuauserv
2. Register the DLL: regsvr32 %windir%\system32\wups2.dll
3. Restart the update service: net start wuauserv

The update service should work again.