Sound Gone!

I've been using MuseScore for a while now, but I never had any problem with the sound until now. The sound for playback is not working right now. I have MuseScore Beta 2. I wondered if it had anything to do with my deleting download files for the program. I didn't think I would need them, but maybe I do after all. All other functions for Musescore seem to be working correctly. I also wondered if it would be good to uninstall MuseScore, and then re-install it in order to get all the download files back, which I deleted. Maybe that would help. (?) However, I must have a way to back up my previous files, in case uninstalling would have an effect on them.