Firstly, XP mode will not run those sort of games, it doesnt support the native installed hardware GPU, rather it uses an crappy emulated intel crap VGA thing. It's aimed at applications and software graphics, anything 3d hardware based wont run.
Secondly it is still 32bit even in 64bit windows 7, as windows xp x64 was such an absolutely unstable mess due to drivers, it was never used for the emulator.