sony mdr-ds3000 detecting dd/dts with pc soundcard

Hi,I'm a forum newbie,excuse me if i not in the right forum.
I bought the sony mdr-ds 3000 cordless headphones recently,and I have a prob with the headphone receiver not detecting the dd/dts signal thru my pc.
I connected a high quality optical cable from the back of the receiver to the front of my pc card,and the receiver only detects dolby pro logic 2 when plaing movies or avi files,and not dd and dts.I have an audigy 2 zs plat sound card which i've been told is dd and dts compatable,i also use powerdvd7 deluxe player.
The headphones detect dd and dts signals connected to a dvd player with no prob,but i watch movies mostly on my pc.I've tried everything in my audigy help files,google searches etc.,but my knowledge is not good(beginner to intemediate)...lol.
can any experts help me out with this?
many thanks