Hi

64 bit is already compatable with most (if not all) recent games.
Sound wise no problems should be encountered there either.
However if talking about Vista 64 bit.
Your board (or more importantly the bios) needs to be able to make the most of what's on offer.
The bios of the latest boards has a 32/64 bit setting.
The onboard sound works well with EAX too
XP 64 has never really been supported like 2000 & Vista.