@Vincent,
Well, all I can think of is perhaps you have overclocked or some setting in the bios is causing trouble. So like mdma said, have you tried loading the default settings?
Most PC's I installed XP SP2 on it worked fine. I did however use a custom install CD (made with Nlite; wwwn.liteos.com) where I got rid of most unwanted stuff (printerdrivers, modem drivers and that kinda things) and had the correct drivers for the hardware that was installed on the target systems.. Took a while to get it totally right tho..
I didn't use the option for integrating any hotfixes tho, you may want to try that on your PC's. If you want to have another go that us.