So lately my computer has just been turning off suddenly without warning. To restart the computer you have to cycle the power switch on the power supply, if you don't, then the computer does not respond to the power button being pressed. Along with this, the air coming out of the Power Supply is very hot. Though what is confusing me is that the motherboard light stays on even when the computer suddenly shuts down. I recently replaced an old ATI 5750 with a new AMD 7950, which uses MUCH more power. I only have a 500w cheap psu. Does this sound like a PSU failure or something else? All help would be appreciated. Thanks.