Windows Movie Maker will play my .wmv videos, but no audio. Earlier today, the same videos played just fine (sound + picture) on the video player app on Windows 8 (don't know the name of the app.) I just checked again, however, and now the sound isn't working there either.

Video volume setting is fine; nothing is muted. I checked the Volume Mixer on my computer, and nothing is muted (I checked both the master volume and the Movie Maker application volume). Audio works fine on iTunes, internet, etc. Are the files corrupted? If so, is there any way they can be saved?  Any ideas on how to fix this?  Many thanks!!!!