5.1 in Source

[PoliticallyCorrect]

i have Realtek AC '97 Audio and i'm getting 5.1 music and dvd's through my 5.1 speakers, but in CSS i get this:

The 5 speakers and subwooder glow red one at a time but i only hear sound out of the centre speaker and subwoofer. The cables and connections are correct.

any help would b appreciated