How do I get my computer to work with my Onkyo 7.1 home theater system?

I have a Dell XPS 400 with the standard sound card. (Blue, green, pink, yellow, and black jacks) I also have an Onkyo 7.1 home theater system. I am trying to run my computer through the Onkyo and when I got it connected I only get sound from the left side and center. I set the soundcard to 7.1 home theater surround sound in the sounds and audio devices panel of the computer and tried all the jacks on the sound card. I also tried every possible combination on the back of the Onkyo, but nothing changes. Will this just not work, or do I need a different soundcard? If so what kind?

How do I get my computer to work with my Onkyo 7.1 home theater system?theater seating

Hello, The green jack connects the front speakers the yellow and black connect the rest of the speakers. i believe black powers the center channel and Subwoofer, while the yellow jack should power the rear speakers. So you need to have all three, Green, Black and Yellow to your Onkyo system. To be able to do this your Onkyo system needs to support these multiple inputs. Most new systems do, however it changes for each reciever. Good luck, try googling it if you have problems.