splitting sound on idt 7.1 integrated sound card to to dvi outputs

I have a pavillion 500-023w desktop with integrated sound and video. the video is two dvi which work fine but the sound from two sources on the extended monitor used the seperate to the front and back green jacks.now they both come out both jacks does anyone know what combination i have wrong and then how to keep it set . hp techs are no help. they say it can't be done . that when you plug into the front jack it disables the rear.