I powered down the computer and then switched the toggle on the rear to off. I thought about unplugging it, but it was connected to my UPS/battery backup, so I figured powering it off would be enough.
I do have dodgy electrical wiring in my apartment because it's an old building, which is why I had the bright idea of powering it off during the storm to begin with.

There wasn't a blackout, but there's a definite possibility that there was a brown out or surge during the storm that night - we get them all the time here.
Since yesterday, when my PC stopped working, I've tried switching the power cord, using two other (non-UPS) power strips I have, as well as a different outlet. Since the fans spin up for an instant (and my PSU is, frankly, better quality than the FoxCONN board), I suspect the motherboard is the culprit, but I'll be thrilled if it's the PSU. The motherboard is discontinued & I don't have the $$$ for a new processor, mobo, RAM and GPU.
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2.4 GHz AMD Athlon 64 3700+ Clawhammer - 2.0 GB DDR RAM - Thermaltake Toughpower 650W PSU
NVidia GeForce 7600GS 512 MB AGP 8x - Sound Blaster Audigy 2 ZS Platinum Pro
1x250 GB SATA - 1x120 GB SATA - 1x120 GB IDE