I'm building this same rig (parts arrive tomorrow). So I'm interested in this topic.

I think XP64 is a better choice than Vista 64 (xp = faster processing & a smaller memory foot-print than Vista).

I may try a dual or triple boot system by adding in XP pro 32 and Linux, each on its own partition. This decision is in wait-and-see mode, as I want to see how many problems develop after I install my collection of 32 bit compiled programs.

Charles