Well, DX10 was originally developed for the XP ME edition (good ol buggy longhorn) before that was gutted and they practically started over to make Vista. In light of that I can see how that's possible. Still, hacking XP like that doesn't always end well. Also, current drivers have alot of optimizations and such for various games to run better on their particular architecture, the main reason modern drivers are so large, so the performance probably isn't too comparable. It would be interesting to see some benches, but I wouldn't really bother installing it myself.