Hey every one, I'm new to Macs, I just got a PC with Mac Os X Snow leopard on it (I traded it for car audio system). Anyways guy I got it from build a PC himself and put MAC on it. I've used for 2 weeks or so and all of a sudden this grey screen with "You have to restart you computer" crap. I don't have the original CD since the guy didn't give to me. So how do I deal with it? PLEASE HELP!!!!