There's test to know if your PSU is fried. The main one, to test if any circuits are fried, is that when you turn on the computer, the CPU fan will give a quarter turn, then it will stay off. It won't take another quearter turn till the capacitors have discharged. I'm sure this is a test for PSU. If it gives a single short beep, or a sort of tone, (a beep, then a second beep with lower pitch with no pause) then it's posting. That means everything is probably still working. I would try a new video card...but then again, if you say that none of your devices are booting up, then it's entirely possible that a small power surge on the cold, or hard, reset flashed the EEPROM containing your BIOS. This would cause the trouble you've mentioned, as basic connections like the fans etc. would still run, but the IDE devices, PCI and AGP devices would just sit there. However if this has happned, it's highly unlikely that you're going to hear that beep. Sounds like some problem you've got there.
What i would do:
Take a good look at my Mobo and make sure everything's the way it should me. This is not a RAM problem, PC's still post and show a boot screen without RAM (beleive me, i know, i was working on a PC and it was almost finished, everything except the RAM, and my idiot brother plugged it in and turned it on while i was out.)
All i can say is what is isn't:
It's not your PSU if it boots and the fans run, unless it's a wire coming out of the PSU that's broken.
It's not a PCI card, but removing them all would be reccomended because you don't want them damaged, and i once had a faulty sound card that gave a problem similar to this.
It's not likely to be your CPU, you would get a boot error message of some sort.
Basically, i think it's probably your Motherboard. Have a good look at it.
-Dave
Your soul...it tastes like chicken
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