I have a machine that has Athlon XP,AGP and a 6600GT agp. It works fine. I re-installed ID 2.0.3. It seems to run fine and would like to run the new OWB.
I know I will have to get a sound card from my other machine for this one, an Athlon64 X2.
This machine has not been tested yet, even though I think I tried it a while back.