64-bit stuff can address well into the terabytes of ram. The only exception to the 32-bit memory limit is using Server 2000/2003 Enterprise or Datacenter.
The 32-bit OS’s and processors are locked at 4GB because they can only address 2^32 bytes. 64-bit proessors can theoretically address 2^64 bytes which totals 16 exabytes but I doubt we’ll be seeing that anytime soon.
Kinda interesting link http://windowssdk.msdn.microsoft.com/en-us…y/ms694080.aspx