I've copied a movie and stored it in my disk drive, and when i opened the movie using my windows media player, it won't play. It said that the required codec for that player or movie is not installed. The movie can be played in other laptops, except mine. I've installed a codec from cnet.com but it still won't play. I don't know what's wrong and I don't know what codec to install. The movie file is MP4. I really need to watch that movie. HELP!