We eventually got that stuff worked out with Newegg, got the parts, and Vicki set out to build the thing.
While removing the expansion slot doors, Vicki broke a capacitor off the motherboard. Newegg replaced it, although that set her back a week's time.
Once all the basic stuff was installed, she gave it the old turn on...and nothing happened. We fretted for a while before realizing that we were in truth, dummies. All we'd done was turn on the power supply...things became a lot more lively once we actually hit the power switch on the case.
For a short time, anyway, as within 30-60 seconds of powering on, the motherboard would give a "total power shutdown" code, and power off.
Disconnecting everything, and then reconnecting it all, seemed to fix that, so now Vicki's newest creation (behind Xavier and Neva) is her own brand new computer. I'll ask her to get some pics, 'cause she chose one of those cases with windows and glowey lights inside.