Need help with dual boot Xp/Vista x 2 Raptors..

I have Xp on one Raptor and I'm trying to put Vista Prem upgrade on the second Raptor. I just reformatted it, installed fresh Win Xp on second raptor it loaded just fine. Installed Mb drivers also after xp install. When i install Vista upgrade everything goes well until It gets to where the desktop should come up the first time. The computer just reboots every time, or I get the blue screen error again and again. What step am I missing. I revert back to Xp on the other drive and everything works just fine there. This build is new by the way only 2 months old now. Everything else seems to be running fine, I have the latest bios installed as well. Am I missing something after I install a fresh Xp copy? Do I need to have the internet working for updates on the fresh install? The Xp version I have is with SP2 also. Im at a loss here,thanks for anynes help!