Well if you are having problems which watching DVDMovies
These are a few solutions
1.> There is a SPDIF Cable which is supposed to be connected to your
DVDRom and your Sound Card.
Looks Like this

It is provided with your sound card and not your DVDRom
2.> DVD Movies have 5.1 Sound and to hear it you have to almost
increase the volume to the max level to hear it.
3.> Download Latest Klite Codec Pack Full Version
Here:-
http://digidownload.libero.it/klitec...lcodec236f.exe
This Klite Codec Pack has MplayerC and AC3Filter which will help
you play your DVD Movies and with AC3Filter your AC3 Audio on the
DVD can be decoded and heard by you.
Go to ControlPanel->Ac3Filter Settings
In AC3Filter select your speaker type properly.
and increase the master and gain level to the max
so that you dont have to raise the Speaker main volume to the max level
while viewing your DVD Movies.
Also What type of Speakers[2.0/2.1/4.0/5.1 etc] do you have connected to your pc
and the name of the soundcard you use
You can also try DVD Playback software like PowerDVD