My PC shut off with no warning, And will not boot up, it will "turn on" but the monitor doesn't show the bootup screen or anything, it stays blank as if the comp was still off. The Keyboard & mouse don't light up/turn on either. Computer is a Compaq Presario. but I am unsure what the motherboard is because we had to buy a new one. PC was used, motherboard was fried, bought new one & new RAM, HD's, everything. Motherboard and ram are under a year old. As are the hard drives. [two 160 or 180 gb HD's one is SATA, other is SATA/IDE] 512 RAM Windows XP SP2. Haven't been having any PC issues prior to this happening. So far everyone is telling me its probably the power supply box. but I'm unsure. Thanks, I will post more specs when I find out what they are.