"When plugging green line in cable directly into laptop, I get 2 channels."
Sorry to disappoint you but that sounds right to me. The user manual for your speaker system says this:
•2-channel sound card: Connect the green plug from the audio input cable to the “line out” jack on your sound card. Do not use the black or orange plugs. With a 2-channel sound card you will not hear sound from the rear speakers.
Because your HP laptop only has a single stereo line-out socket, you can't connect the black and orange plugs, so I can't see how you're going to get surround sound (or sound from all the speakers).