I'm so confused my pc has been working for ages with no problems then all of a sudden it will restart ( or sometimes it will fail to restart ) or the screen will go black and pc stops working. I thought it was my graphics card because I put it in a friend's pc and it did the same thing. I bought a new graphics card and all seemed well for a few hours but then it it started doing it again. I don't know what to do any help would be really appreciated.