they use different serials. you can find them out there on the web though. I found a working one, so i know theyre out there. IF youre going to use a hacked winblowz XPee install though, make sure its XP PRO. XP home requires internet activation with a working serial (it sends your serial to microsoft via the internet). and its somthing like every 3 hardware changes you have to re-activate it to prevent piracy. XP pro was designed so that you could readily put many copies of XP on different machines and upgrade etc without reactivating it. so XP pro is basically XP home only a little better, and you can get around contacting microsoft. if you use XP home, you will need a program to crack winblowz XPee and work around the activation. its a nobrainer really. get Xpee Pro, and find a serial using google.
Actually you dont' have to re-activate it at all because I'm using Win XP Home that came w/ my parent's Dell and we just took the serial from the dell and typed it in and activated it and it is working perfectly.