Windows MovieMaker file not playing when saved

I have 2 Movies saved for playback on my computer. The one movie plays perfectly but the other one does not want to play and has no audio. This second movie plays perfectly on the timeline or on the storyboard, but once I save it as a movie file for playback on my computer, it does not want to play, and only shows the first clip of the movie.
The only possible cause could be some ‘data updates’ that was done on my computer since I made the first movie. I know I should be more vigilant, but I work at a university where we have ‘data updates’ done on almost a daily basis, to prevent viruses, security breaches, etc, and I don’t always take note of what updates take place, but just restart my computer when instructed to.
Ever since the last data update, the movie files created does not want to play. The one movie, created before the last update, still plays perfectly, and now uses Winamp to play.
Both movies are type Winamp media file
Any advice will be appreciated!

I think you need to install some codecs to play the different types of media. http://forums.techarena.in/windows-software/1072187.htm

There are a bunch of posts on various board about this same problem. Looks like we're stuck waiting for Microsoft to fix the problem. It makes me want to go out and buy a real movie making program.