My friends computer has been having problems recently which consists of his computer (whilst playing games) crashing (the game), his monitor going black/grey which would be solved temporarily by restarting his computer. This also seems to be a common occurence when I am in a call in skype with him, however it seems to be only me that this happens. The specs of his computer are: Mobo: Gigabyte H87-HD3 RAM: G.Skill Ripjaws-X 16gb 1600MHz SSD: Intel 530 series 120gb PSU: CX 750M Corsair CPU: Intel Core i5 4670K HDD: WD 1TB 3.5" GPU: MSI Nvidia GTX 780 If you need me to give any more details I would be more than happy!
If I had to guess I'd say the PC is over heating or the graphics card is faulty. Try installing Open Hardware Monitor and taking a note of what the temperatures are when the PC is idle, then run a game in a window and take a note of what the temperatures get to before the PC crashes. I'm thinking its either the graphics card or processor that is overheating, you could open the PC and ensure neither is clogged up with dust. Also you could swap the graphics card out the PC and put one in you know works ok from another PC. If the PC works ok with a different graphics card when gaming, you have found the graphics card is the problem.