i have to be the person who always brings xp down...
when i upgraded my box from 2k to XP, i noticed a slight *decrease* in 3d performance...i had run 3dmark on 2k (on the same system) before i upgraded, and then ran it after i upgrade to XP, and there was a huge difference (15-20% faster is 2k). take it with a grain of salt, but i'm not completely sold that XP is better for 3d or games...