Quoted from ExSquid:Got a power cord, it still wouldn't turn on, I called IT tech support and turns out the small battery on the mother board CR 2023 or something like that was dead. So I can only turn my machine on now with the "soft" power switch under the top of the cabinet. Until I replace the battery. And that seems like its going to be a pain in the ass.
I just had the same thing happen 2 weeks ago and thought my power supply had died. You can get the battery from just about anywhere, amazon etc. It just pops out and pops back in, takes about 2 minutes to fix with most of the time being spent taking the cover off of the computer.
Until then I had to jump the pins on the motherboard since mine is a cutdown and doesn't have a soft reset button. After that make sure you go into the bios and tell it to boot on receiving power again and you should be good to go.