After you have installed the Windows XP SP2 and want to use the windowsupdate service, then you would be taken to the new v5 of the service at http://v5.windowsupdate.microsoft.com.

In this version 5, Microsoft has made sure that pirated copies wouldn't be able to use this service. More pirated keys have been added to the blacklist and it seems that Microsoft is using a more thorough check of the copies of the users (and copies) who would be using the WindowsUpdate service.