If you're using the built-in media-player component that ships with flash-pro IDE's, there is a property which you can set to false to stop the video from auto-playing.
I can't remember exactly what it is called, but from the flash IDE, if you select your instance of the media player component on the stage and then open the component inspector window (or was it the properties window?? Been a while since I used the flash IDE now!) Either way, somewhere in the properties or the component inspector, you should see the auto-play property. I think it's set to true by default.
Set this to false and that should be all you need to do to stop the video from auto-playing.