i am running a dual boot system with Win XP pro 32 bit and Win 7 64 bit..Im not sure if it's just me but i have to say Maya 2011 runs smoother and faster on the xp than it does for me on win 7 .Obviously the 64 bit is better for things like simulations ect where ram is needed but for general modeling i prefer the xp as i dont like the slight delay i get with win7.