How to view a video device through the component video input through Widows media center?

trying to hook up a external video device to the composite input on video card. there is no option in windows media center to view composite video. is there another way?|||what kind of vid card is it alot of vid card are output only unless its a video capture card i have a tv tuner and a video capture card in my comp and it dont have any trouble seeing composite video from my dig camera