Ahhh, thanks! That's VERY close, mines a P5Q-E, not a 3 though.. In that pic at the top left there's a 2x4 that's half plugged. The open 2x2 part is where the 2x2 connector on the PSU fit when I tried it.
I'm gonna put things together now and try it.. There's no ram, so it won't POST, and I still need a video card, but this is interesting. For a minute there I thought I was gonna have to spend a cent on this ultimate budget rig.. Phew!
PS the wife had the bright idea today to say "Well, if the DDR2 for that board is more expensive than current DDR3, would it cost much more to just build something current?" I married the right girl!