a couple of weeks ago my computer was on and the main power was turned off to my house. Since that time when I try to boot the computer on it may come on or it may not. If it comes on, it might stay on a minute or 8 hours. The screen goes black. The fan on the power supply is the only thing that is running. This is an eMachine 2042. Tech support said it was the motherboard. Does this sound right?