No sound in Windows Live Movie Maker

Somehow the sound got turned off in Windows Live Movie Maker. The computer has sound in other applications, but in Live Movie Maker there is no sound, even though the volume is turned full up, when I click the "Video Volume" it shows a red circle with a red line thru it indicating the sound is turned off.
It worked in the past, I used it to make movies. How do I turn the sound back on"

If everything else works OK, I would suspect a problem with the Movie Maker. Try reinstalling that and see if it fixes it. You may have to uninstall it, restart the PC, and then download it from Microsoft to reinstall (do not skip the PC restart - if you just uninstall and reinstall without restarting the original problem can still be there).