Well, the board I have is the Shuttle AN50R. I've really liked it so far and it was AMD recommended.
I have two drives in the machine. One is a 160GB SATA drive, the other is a 40GB ATA. The 160GB drive has XP Pro on it, which I rather not touch, being that out of the box my XP Pro CD had no idea what it was. I partitioned the 40GB drive into 3x13GB, after the Server install failed.
As for XP 64, I have it on the first 13GB partition right now and for me, its unusable. It didn't have support for my on board components and wouldn't install from the mobo CD. If my board didn't have optical audio, gigabit lan, and regular lan that I really enjoyed/needed, it wouldn't be quite an issue, but I have my XP Pro side Rendezvous sharing from my PowerBook over wireless to iTunes for PC, then I have a 12' optical cable running to my theatre system. Needless to say, I'm quite used to being able to access music from any of my machines and play it at "full" quality, so I severely miss it...not to speak of the fact that I can't seem to get the network devices to work.
I see on AMD.com, they have a listing for 64 bit Server 2003 for Opteron...think I'd be better off trying to download that one and installing it?