No Wifi, as it simply doesn’t have a wifi adaptor.

Ethernet is a possibility. I tested it right now and removing the Ethernet cable doesn’t cause a wake-up, but I suppose it’s possible that slight interference if the cable were just slightly moved might cause it to register traffic plus a continued connection, enough to cause a wakeup. I’ll try tinkering with that, thanks!

My computer turns itself on when I walk through a certain spot nearby it.

“Ah, you must have your mouse or some other peripheral set to activate it and the vibrations from walking-” Nope, I know how to disable wakeup from peripherals. “Well, then the vibrations from walking must be disturbing a loose component inside-” Nope, problem existed through a near-complete teardown and OS reinstall. Also, putting the PC on vibration isolating foam did not help.

At this point, I’m down to two conclusions:

• The wire for the wall outlet runs under the floor, and vibrations are causing adequate power fluctuations to wake the machine up. Not sure how to test for this, though it does concern me about the state of the wiring.
• The PC is haunted.