Media Center/Media Player Conflict

> When I stick a DVD into my almost brand new dell media center computer, it
> auto loads windows media center to play the DVD. For some reason, it will
> take a wide screen movie and make it fit the whole screen. I have even
> played
> with the settings in the program, but it doesn't fix it.
>
> Main problem: after auto loading in media center and exiting out of that
> to
> play the movie in windows media player, it can't display the video in full
> screen mode, even though when it would it would do it correctly. I would
> like
> to disable media center from auto loading. I wonder if the two programs
> are
> fighting with the video drivers. But then I don't know. Any help would be
> really great.