Old PSU got fried after a large lightning storm. I don't think any other hardware was damaged, but it's possible.
Installed the new PSU, now turning on the system seems to provide power to the motherboard, but ide drives don't spin up and the system won't actually turn on. The LED on the motherboard turns on, peripherals have power (keyboard LEDs work, as do the LEDs on the NIC), and the CPU and PSU fans both turn on.
I've taken out all unneeded items, it's just down to the CPU, video card, and RAM, but it makes no difference. The system basically sits there in a "half-on" state, it doesn't appear to be shorting out anywhere.
I've also tried a known-good power supply, an old pci video card, and have reseated the power supply connection on the motherboard numerous times, but all seem to have no effect.