CPU or Motherboard... Whats broke?

[Bradley99]

Hey guys so the other day I left my PC on and went away for an hour and I came back and it was in the BIOS. I told it to boot of my HD as it was for some reason set to my USB stick. I restarted it and then it said no signal to monitor about 10 seconds later it crashes comes back on and does the same thing but this time it stays on but all the fans spin up and light up and it sounds normal but just No Signal to Monitor... I tried another GPU, Tried the paper clip test with my PSU and tried swaping the way the RAM is seated around. The CPU fan is on so the only 2 things it could be are the CPU itself or the MoBo. I took the CPU out and it looks fine same as the MoBo.... Also the USB ports are not giving out enough power to power my mouse and keyboard to so is it the mobo?

[rhyseyness]

Have you tried a different monitor (or different input to that monitor)?

Also have you tried a different display cable?

[That Norwegian Guy]

You left your computer on, (logged into Windows I presume) you walked away and when you came back it was in the BIOS?

 

Was there a power outage? If not it sounds like HDD failure. Though the computer should post... Still.