mpeg problem

Hi
I have a strange problem with my windows media player (version 9). When I play mpeg movies the screen goes all black and I can’t see the actual movie. It’s strange because I can hear everything but I can’t see anything. I’ve tried all my mpegs and none work. It was working fine until today. Does anyone know what is wrong, if so please help me.
Thanks

If no one knows what is wrong, then can someone please tell me how to re-install windows media player. I wouldn’t have a clue how to do it besides formating windows which i cbf doing.
Thanks

Go and download drdivx on drdivx.com and it will play almost all types of video