Windows Movie Maker is the most broken and buggy piece of shit ever created. It's notorious for freezing, crashing, and being incapable of any sort of complex editing. Seriously, it only has one audio track! FUCKING ONE! If you want music AND sound effects, you have to export your video twice! Also, good luck doing any kind of motion graphics or video in video. MS Paint is all ya got for that.
In all seriousness, it's an easily accessible and simple program that Multi used to edit his videos until July 31st, 2012 when he upgraded to Cyberlink PowerDirector 10 and then subsequent programs.