I had a problem close to that. My volume wouldn't show in the toolbar and the sound wasn't working with any music or videos. I messed around with the hardware wizard and uninstalled a sound drive that wasn't working. It went back to normal after that.
I recommend you don't do this, though. My computer is old and out of date so I can mess with it. I don't think you should do that unless you know what you're doing and you really want the sound, AND if it's a last resort.