Successful upgrade from A64 3700 to A64 X2 4400.
Opened case, swapped cpu, closed case.
Fired up windows. It detected the second cpu. Rebooted.
Installed dual core driver and optimizer, plus some MS hotfix I read about somewhere. Rebooted a few times.
AH runs just fine. Able to run 4x FSAA now, with FRs locked at 60 using 1280x1024 resolution and high-res textures. 6800GT AGP vid card, 2 gig ram.
Nice little upgrade overall, and fairly cheap too with the recent AMD price cuts.