Ideally you'll need to know what soundcard you have.
It's most probably because the settings aren't correct. If you're sure you have an Audigy 2 ZS sound card, then you need to have the creative audio drivers installed and the software (EAX Console etc...). Should be provided with a CD which comes with the soundcard. If not you can download and install the driver for the SoundBlaster Audigy 2 ZS soundcard here: http://uk.europe.creative.com/suppor...ype=0&x=25&y=5
which has bundled with it the software required.
Stereo / 2 Channel audio can be upmixed to surround in the EAX Console by enabling CMSS, and choosing an upmix method.
If you're watching multichannel DVDs through WMP, you need a multichannel filter/decoder...such as AC3Filter
. It's a popular filter capable of handling multichannel audio on DVDs for Windows Media Player. You can change the settings of the AC3Filter in WMP by going to Options
Tab > Advanced