Sound just wont work on 5.1 sorround (PC)

Hi Guys.

Been having this problem for a long time, but since I used the amplifier through my old tv before, then now I'm forced to use it through my computer, since I got a new monitor, which is a pc monitor only and not TV/PC.

So what I have, is a toslink cable from my amplfier, going to my pc. The tv and dvd player is also plugged in the Amplifier, but they are working fine. But here's the problem:

Even though the toslink cable is plugged in the computer, there's still no sound. I tried updating my drivers (2008 now), try to plug the cable in the other normal audio inputs (Line in etc.). It did find it, but still no sound. It just shows that the cable works, and it can find it.

So I'm pretty much lost here. Got no idea to do. Before i used the speaker from my TV/PC, and since my TV was connected to the amplifier with another cable, it was no problem. But I already tried to use the speaker from my TV/PC, but it wont work, without the TV/PC is also plugged in as a monitor.

I have tried a bit of each, but nonetheless, nothing worked. I really don't see what to do, so any kind of help would be very much appreciated.