Creative s750 and onboard sound card set up problem

[Combat squirrel]

As title, I have this speaker set, and im trying to make the PC output 7.1 to my s750's, hardware is:

Asus P5Q Pro
Creative S750

Now, the issue is, the cable I have for the speakers is 3 plugs at one end, 4 at the other, 4 plugs go into the speaker amp, the 3 into the pc............NOW the issue iv noticed here is, the cable colours are black, green, orange and grey, iv plugged in the appropriate cables in the right places, but the back of the PC also has the grey cable out.........where at the pc end of the cables its missing grey, im guessing this was creative proprietry design for there cards only...

Now I then got a standard phono to phono plug to link the 2 grey sockets, and this hasnt worked either.

Im missing rear left and side left speakers

I also have a creative DDTS100, but I cant see how I could make all that work either to try and get the 7.1

My only other option is pick up a pci-e creative sound card I guess and do optical out to my ddts100 and then onto the speakers.

Am I missing something obvious here ? How can I get 7.1 output from my pc to my 7.1 speakers ?

 

[Combat squirrel]

problem solved was a dodgy speaker cable

 

[Monkeynut]

Simplest solutions are the best.