My wifes computer has a intel quad core with a decent gfx card. She has the i5 and the gfx card needs a 400 wat power supply. She has a 750 wat power supply. She was using her computer and the sound stopped working. She rebooted and then the computer would turn off and shut off for 3 seconds. I made sure all the power connections were connected properly externally then I opened it up and everything was connected inside. I reset the cmos jumper and then reconected the computer and it worked. Im assuming it is the power supply but I have not tested it with a new power supply.