Computer won't turn on, psu suspected

[Voodoo89]

So my computer refuses to turn on. I've been using it for about half a year now, but recently went on vacation for a few weeks, and when I came back it wouldn't turn on. The led power indicator would turn on for a split second, then turn off. After pressing the power button twice quickly, the computer did turn on but the PSU started emitting a high pitched noise. I turned it off, dusted everything, then turned it back on (same way) and the problem persisted, moreover, I noticed that while the computer was off (but plugged in and the PSU turned on) the PSU emitted a low humming noise, which, when I unplugged the computer, faded out after a few seconds. Now the computer won't turn on at all.

Specs:

Antec SP-500 PSU
Athlon 3200+
EVGA Geforce 7800 GT
1 GB RAM (2x512)
NForce 4 motherboard
Hitachi Deskstar 250 GB Hard Drive

Help Please.

 

[Chernobyl1]

It does sound like the psu is damaged.
Maybe the power went out or there was a lightning strike while you were away and it caused the damage.

I'd test with another psu before declaring it dead, but that sounds unhealthy.