Movie maker, sound doesn't work on my videos

I can't get the sound to work with my videos. Does anyone know how to fix that? It works fine on my computer when I play it but not on the movie maker! this is important , it's a school project! also can windows movie maker record sound as backround, my voice I mean?

but make sure you imported the song into collections right
and the song doesn't have red X's on the timeline
then go to the timeline mode and the first icon on the left right above the timeline is like, an audio level button, click on it
and then it has a bar where you can adjust the song to the project
then next to that button has a narration one you can record your voice
hope this helps

yea this happened to me... try importing the files from an outside source such as your mp3 player or a flash drive. if that doesnt work, you might just have to do a system reboot.
But before you do any of those things, do all the things foxxxy18146 suggests...