You purchased a card who's performance is solely dependent on the efficiency of the crossfire drivers is the problem. That, and you're still running an obsolete OS.
Uhm... i wouldn't say obsolete, but, for a M$ OS, "rock solid" comes to mind :P
Vista still is struggling to get a lot of things from XP to work fine. Wich, btw, in XP work very well indeed.
So, don't say "obsolete", cause that word is not even close to describe XP.
PS: Was that flame bait, anyway? xP