hi there richard. I’m using vista ultimate 32bit at the moment, and as an OS, its VERY ram intensive. I’m currently running a quad at 3ghz, 4gigram and its working just fine (and i’d think that your rig would handle it fine too).
Sorry I don’t want to comit anymore than that because I know there are a lot of people here with FAR more experiance than I so they will have a better answer, but I’m happy with vista 32bit.
-Dave