Clean the complete inside of your tower with compressed air, this used to happen to me a lot, it means that your Graphics card is quite dirty, and it will start happening with other things so clean it,
Before i knew this was the cause, i was soundless, Videoless, and almost powerless. I had to open 5 windows to get the cloud of dust out, it was like The Mist, but made of brown crap, in my house.