I have a Dimension 4550. I have sound but it is very, very low.  I have checked the volume control (in all places including control panel) to see if it is turned down or muted. It is not. The problem started when I had my headphones plugged into the front of the tower. Finally it would no longer work so I moved to the back of the tower. This worked for a while, however, sound only could be heard in one ear. Now, the sound it only loud enough that you can tell it is making a noise but you can not understand it. Any suggestions?