Partly dead power supply or something....
 

My desktop won't power on this morning. It was shut down normally yesterday afternoon.

No beeps, no leds flash, nada. Like the power button isn't functioning. I tried to (momentary) jump the power pins on the mobo, but that also had no response at all.

The PSU, (Antec sp-450) which I thought was dead, makes a very quiet squeaking fan noise when the toggle switch is on. The noise stops, obviously, when the PSU toggle is off or when it is unplugged. So it seems that I have power going into the PSU, but none coming out.

It may also be worth noting that this system had a bizarre practice of booting up when unattended. I would shut it down and go to bed, and it would be running in the morning. I never figured it out, but it stopped without explaination.

I don't have easy access to a spare mobo or psu. I may be able to get access to one or the other if I try hard enough. Best course of action?

Replace the PSU would be a start. None laying around? All you've got to do is plug in the mobo and see if it boots.

I would disconnect everything but the motherboard AND the power supply.

If the power supply starts then you can look elsewhere.

Thats where I was at when I started the thread. Well, not quite. I hadn't unseated the CPU yet, but have since then. No luck.

I've talked to a computer savy friend of mine. We're going to try some PSU and mobo swapping tests on tuesday night when we are both free.

Alright, but KISS first and just try the PSU before you even think about unscrewing the mobo :)