sound stopped working

[hhead]

My sound has stopped working videos, mp3's system sounds the lot. Done a few uptodates on system over the last few days, one of these must have broken it. Haven't a clue where to start...

[hhead]

Uh started working again, I was writing a blog entry and the computer made a sound. Haven't done anything. I'm not sure whether to put solved. Also politely how do you do that?