well XP CAN utilize 4 gigs, if its 64-bit. and actually the box and ps3 versions were pretty crapped down to fit the console's power, i guess they will just restore some of the former quality and make decent optimization.
Uhm.. Restore what exactly??? It was made for those consoles. Anyway, I wouldn't worry so much. You'll probably be able to play it fine. Don't think it's going to be insanely demanding, like some seem to think.