Yeah. Sounds similiar to my computer problems I had a few months back, which was a PSU fail. How old was the computer/PSU? Can you boot to see BIOS post beeps? If so, try to get into bios and look at your voltages on your rails (I was able to do that, thankfully, which is how I pinpointed it down to my old PSU being all out of kilter (15v on a 12v rail? Dat's way out of variance).
If it is PSU, hopefully you had a reputable one-- a PSU fail can fry the magic smoke and make the whole computer be a glorified paper weight (how do I know this, you ask? Its happened to me :/ Is why I overkill like whoa on PSU and ALWAYS go Corsair or Thermaltake, silver to gold rated efficiency, they have breakers in the PSU to shut the shit off if it goes bad)