So I turned my computer off today and the sound isn't working, I don't know the reason, Worked fine yesterday. So when I go to preffs. and look for the internet sound output it says no units found? There is suppose to be something marked there but I don't know how to find it.

There is a sign that looks like an O with a line above it, One like the STOP sign. When I try to mute or un-mute it works but the stop sign is there preventing me from hearing anything, I would apreciate any help.

Example Picture:,r:0,s:0