I have a MacBook Pro (2 years old). Have Windows XP Pro on it (need it for office programs) - it's 32 bit. Computer has 4 GB RAM. I'd like to upgrade to Windows 7 Pro (or Ultimate) - however, I am not sure if the 64 bit will work (be compatible with my current XP 32 bit version). I've read that if I have 4 GB of RAM, it should be OK no matter what version is on there, however, want to be sure before purchasing.