Hi friends please help me.My computer is shutting itself off.it just shuts off as if i were to press and hold down the button on the tower. it only shuts off at certain times. it will stay on for days if i only go to certain websites, but if i try to go play a game or something that requires more energy or time, i don't know, it shuts off. i ran virus scan after virus scan and it still does it. I don't know what to do. need help.