Xeon processor?

AFAIK the current ones are basically just Core2 chips with more cache and some additions to support multiprocessor systems, so I'd imagine all you really need is a LGA775 board with appropriate BIOS support. As they're designed for servers though, there's not really much point using one in a desktop system (you're highly unlikely to need that much multiprocessing power outside of a server context).

Edit: looking further, it appears that the newer ones are moving off of LGA 775 to a LGA 771, so you'd need a special server board in that case.

You need a server class motherboard. Tad more expensive than your average desktop motherboard.

Thanks guys, that's all I really wanted to know...