In point of fact you can use either the 32-bit or 64-bit version when you buy a SQL server license (so long as you don't use both at the same time, of course). With only 4Gb of RAM I would agree that there's little point using the 64-bit version, but if you might upgrade the RAM at some future date you might as well install the 64-bit one now rather than have to do an upgrade installation later. (You would need the x64 edition, by the way--IA64 is for Itanium CPUs).