>4GB drive usage is not hampered by whether the OS is 32-bit or 64-bit.
There is a limit for 32-bit setups for RAM, being 4GB, but that's because RAM is talked to and referenced differently to hard disks. I can't give you a definitive and correct explanation as to the why's and how's, because I don't know :-)
IIRC, I'm not sure, but isn't the 4GB drive barrier addressed in OS3.9 or 3.5?
