http://www.mp3load.ws/mp3-encoding-programmes/

Problem Uploading Windows Movie Maker videos to YouTube?
I recorded an audio track on Audacity. I then exported it as Wav. I took a few pics from google images and created a pic time-line for the audio.
When I tried to upload the video to YouTube it said “File Format Invalid: The file you are uploading is not a valid video file.”
I tried to use Bonk Encoder to make it MP3 but it also doesn’t seem to recognize the file type (Which is stupid, seeing how its WMM).
I couldn’t export the audio file as Wav because I couldn’t find and download the right encoding program.
Anyone know how I can get around this? Perhaps a way to convert my WMM movies to MP3?
That WMM or MSWMM is a project file, not a video file.
What you need to do to access the File menu and from Publish Movie you can output a WMV file which will be a valid video on youtube.
Here are the base instructions on how to do that:
http://windows.microsoft.com/en-us/windows-vista/Publish-a-movie-in-Windows-Movie-Maker
Lame MP3 Encoder Install Tutorial