Problem in saving a video in movie maker

I use Windows 7 ultimate. Recently I wanted to make a video from windows movie maker.......I saved the file in .wmv format and it was saved successfully. Now ,when I try to play the file,.....the video doesn't show up,....all I have is a black screen. I saved it in the mp4 format,....but again encountered the same problem.

I updated the driver software ,for display........it's showing up to date...& still nothing is helping..