Movie Maker tends to corrupt or stop working after a while of making it work with various file types.
It's inevitable, and Movie Maker is by far the worst program for videos....it's poorly made.
But anyways, just Google the word K-lite Mega Codec Pack
There should be some links to downloading this Codec Pack.
What this is, is basically a decoder for your computer to use when importing files to programs.
It's pretty handy, free, and doesn't take up far too much space.
Once that's done, you should be able to drag in the songs (mp3, avi, etc..) into Movie Maker easily.
Just don't overdo the amount of files you convert.
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