Issues with surround using g51 speakers

[rebel00]

I have just purchased a set of logitech g51 speakers and have connected everything correctly with the via version 5.4a of codec type vt1708b. The problem is that the audio doesn't read as 5.1 sound. When performing the speaker test within the audio deck, all the speakers that are connected correlate to the appropriate satellite and produce the demo beat given. When trying to listen to music through windows media player or play counter strike source it wont give me any rear audio output. I know that it is correctly input and that sound can come out from there, but am wondering why even though I have this 5.1 capable card that I am unable to actually experience it?

Any help would be greatly appreciated.