Video taken by smart phone and edited into a 2-minute movie by Windows Movie Maker. Both video and audio play well when it is PREVIEWED before saving the movie. But it plays ONLY THE AUDIO without any picture but a black screen if the edited movie is saved. The PC on which the movie is edited: A desktop with Windows 7 Pro. 64b. Do not know the problem nor how to solve the problem. How to make the movie play both video and audio ? Thanks.