Their is a great freeware program, if the http://www.jfwlite.com page is 
still there.  The program is quickmix quick audio mixer.
What it does, is to create a file with your current audio settings.  You can 
make multiple files, and then make a hotkey to one of them from your 
desktop.  That way, if you loose sound, press the hotkey and your 
functioning audio settings will be returned.  I use the program for 
selecting different audio inputs and audio levels.  Files like mike, 
turntable, vcr, and web.  The names tell you what they are for.