Thread: Game Startup Error

Ok, First answer i'll probably get "Whats you pc specs?" so here it is:

OS: Windows Vista 64bit Sp1, Graphics Card: ATI Radeon HD 3650, Processor Intel Core 2 Quad Q8200 quad-core, Ram: 4gb DDR2, Harddrive: 688gb

Ok now that that's out of the way to the issue at hand. Ok so before I could play Left 4 Dead without any problems then about 30 minutes ago I decide to boot it up and play some campaign then it the game loads the screen goes black then it minimizes and goes back to my desktop, I can hear all the sound and stuff and when I alter my screen resolution then bring the screen back up I can see the intro video for like a second then it goes back to my desktop, I Ctrl Alt Delete to close it then it says the program is not responding even though the video and audio are still playing, I've been looking all over the net to find a solution but have not suceeded so if anyone could give me a helping hand that would be awesome... and no I didn't alter any files within the game directory or anything like that.