No browser sound, audio mixer problem

Dear sirs,
I have a problem with the sound mixer. I can't hear sounds on on-line videos (all browsers). I have searched on internet but I don't found anything helpful. After all, I watched my sound mixer when a video starts on an browser (there must be on the mixer the browser sound bar) but there wasn't nothing. Anybody know how to repair this?
Already tried to reinstall flash player, sound drivers, check internet options (everything was OK), reinstall browsers, install K-litle codec 64 ...etc, but there is no sound. Offline everything with the sound is OK.

Any ideas?

Thenks

restart your computer and at the first screen enter the setup mode (f2 or whatever it may be) then go to advance and one of the settings might say mute only well change it to normal hope it works

I did that, but everything was OK there...nothing on MUTE or DISABLE.
Still no browser sound ...