Right now im running the windows 7 rc 64bit on my desktop. I tried windows xp on my desktop and for me it just made my pc so slow same with windows vista. My specs are 6gb of ram, 280gtx 1gb , i7 core 920 and a 1tb hd. I also installed windows 7 on my laptop and everyone in my house loved it. It's smooth, no more lag and what not.