Fail to Install updates after installing Win XP SP3

Just go to C:\Windows\System32 and find and register Wups2.dll.

To do that, right click on it and select 'Open With' then 'Choose Program' and find C:\Windows\System32\Regsvr32.
If you choose to 'Always use the selected program to open this kind of file' then all you will have to do is double click on any .dll to register it.

Once you have registered Wups2.dll your problem will disappear.

I hope this helps.