The motherboard is a Asus P5Q pro with a built in sound card Realtek High Definition Audio.
I tried to connect the front speaker (green jack) in the green plug, the rear speaker (black jack) in all the other plugs but i couldn't obtain a quadriphonic audio...
I can't use the rear speakers in a Cambridge soundworks fourpoint pc system ( http://ec1.images-amazon.com/images/P/B00000JDH5.01._SS500_SCLZZZZZZZ_V1056649218_.gif ) I mean, the front speakers work, the subwoofer works too, but the rear speakers don't work. I tried to invert the speakers...