i'm not sure why 64 bit hasn't become more mainstream, but i think there's just less software written so far that takes advantage of it. some people seem to be running it just fine, but just make sure all the software you normally run will work on it. i am running 32 bit vista and will have to see next time around if i go to 64 or not,,i would probably just stick with 32 bit for now if i were you, but maybe some people using 64 bit will comment also.