Hi
I bought this new system Logitech X-530. I installed it like the manual said : plug the orange, green and black wire into the same colored inputs on mobo. I did, I pluged the channels wire into the subwoofer and pluged the sub into the outlet

( mobo = Abit nf7-s )
When I start winamp or a game I don't hear the center and rear speakers. Why ? In control panel, sounds and multimedia, sounds, advanced. The setting is 5.1 Dolby Digital. In my nvmixer (nvidia mixer version 1 build 431) The setting is 5.1 Speakers Dolby Digital. If I set it the 5.1 Speakers, nothing happens.
What is wrong? help
Thank you