64-bit will only work on a 64-bit cpu. Not sure how good the performance difference is, but if you have a 64-bit cpu, may as well use it as much as you can, so 64-bit OS is good place to start, but to see the real difference you'll need 64-bit apps. tbh I don't know whats taking so long for 64-bit to be adopted, but now, its rather hard to find stable 64-bit apps. With 64-bit windows you'll have trouble finding drivers too, so just keep that in mind. If everything is setup and works, I would say just leave it.