DVD CDRW WILL NOT PLAY SOUND

Question

I have a acer aspire 3500 with a matshita UJDA760 DVD CDRW and it's saying that all my drivers are good and up to date, but when I put in my DVD's they play but I don't have sound. I put in a cd and it ripped the songs and when I hit play I got sound but when I put in the dvd it is still not playing sound. The picture is perfect and everything is find except sound. I tried playing the dvd with windows media player and realplayer. They are both doing the same thing.Can you help me?