Today I got to my computer and it was completely dead. So I switched out the power supply with another computer. The power supply didn't work in that one either so I just figured it was dead. I put it back in and now the computer works fine. Any idea on what would cause it to not work for a 12 hour span? Sometimes the computer will randomly turn off, but only in the middle of the night if I have accidentally left it on and only every once in awhile. What would cause this?