Like the other poster said, unless you have some specific game that you are just shy or running full speed, there is no point in going to 64 bit. Also, depending on the level of customization in your setup and what additional games/emulators you run, going to Win 7 x64 could pose incompatibility problems. I actually switched over to Win 7 x64, got fed up with all the issues I had and switched back to XP. Again, this depends on your setup. MAME would not be a problem.