Thanks for addressing my problem.
I used my android smartphone to record the movie including sound. This ended up in a mp4 file which I transferred to my laptop running Win7. This file plays perfectly on the laptop using virtually any of the known player softwares. When I import it into Movie Maker it plays it perferctly. So there is nothing wrong with the original movie. But when I get Movie Maker to save the movie, even without any editing, the saved mp4 file does not have any video - just sound. Movie Maker allows me the option of saving the movie also as a wmv file - but this ends up with exactly the same result of missing video and a significantly reduced file size. Any software including Movie Maker itself plays only sound and no video - just as a result of saving. So clearly, the video is missing from the saved file.
Please note that I used the "save movie" function as I do not even understand what "save project" means. Also, in saving, I have tried just about every setting that is available such as default, HD, DVD, YouTube, Win7 etc.
What could the problem be? Help