can't mute. everything else seems fine.

everything was operational, i did not install any new programs, but from one day to the other, my "mute" button does not work anymore. i can manage volume and the media buttons (play/pause, ff, etc) also work. the only thing i can't do is mute. so weird... i thought about updating (again, since the win7 upgrade had it updated) the quickset software, but i can't find it in my system, that is to check the version number.

sorry... i have an inspiron 1525