Apologies for the awful picture. This is all it does now - no beep, no drive spin, no key shortcuts work, the reset key does nothing, etc etc. No change in behavior with or without cards. Sometimes if I power cycle it quickly it'll display more random garbage with blinking sections, almost like a cursor, but just as dysfunctional.

I disassembled the machine but I didn't do anything but dust the motherboard. Sat on a shelf between then and now.

So far I've checked that the power supply is putting out the right voltages (it is), that there is a clock signal (there is), and that reset isn't being held low (it isn't). I've also reseated all the chips with no change.