Hi wannabenerd and welcome to Vista Forums
The retail versions of Vista Ultimate, both the upgrade and full versions, come with BOTH 32-bit and 64-bit versions of the OS on separate discs. They are now available with SP1 already integrated. Make sure that you have the latest drivers for your motherboard (burn these onto a CD for ease of use). As regards the memory, check with the motherboard manual for details on how much is supported and at what speed.