(via www.ubuntugeek.com)
If you have just upgraded to or installed Hardy or Intrepid or Jaunty and you have some sound somewhere, but not everywhere for everything, this is a fast way to get all the missing stuff you need and give you some tools to figure out what is going on. If you hear the startup sound but nothing else, or if some applications work and others don’t, this is for you. If you have no sound at all, there is a link at the end of this post for more extensive troubleshooting help but you should try this first anyway as it may solve your problem and will not make matters worse.