I have Windows 7 Ultimate, and I installed the game Mafia (developed by Illusion Softworks). The game worked perfectly, but since I've had reinstalled Windows 7, there's a problem with something - I can't quit the game, when I confirm, that I want to quit, the program crashes - the screen doesn't display anything (a black screen appears), and the computer is not responding(even when I press CTRL+ALT+DEL or similar). I tried to disable Aero, but it didn't help. The only way to shut down the system is that I press and hold the power button. Since yesterday it happens not only when I want to quit the game, also when I only play, sometimes the picture dissappears, but the sound still plays. In this case I also can't quit or shut down the system. Does anyone now, why this happens, and how to fix it?