5.1 issues

I just recently bought new speakers for my computer (Logitech X-540) and upon hooking them up I ran into some problems. I can only hear sound while using Windows Media Player, and then it only comes out through the front middle speaker and the back ones. While on YouTube or any site like that I can't hear any sound at all, and while playing games the only sound I hear is ambience. I've tried friggin around with things but nothing seems to work. I'm thinking its a problem with the on-board sound (ASUS P5B) because thats also the source of my headset troubles (can't talk through it...).

As you can see I'm almost completely useless with anything computer related, so the solution may seem obvious to those who read this, but if anyone has any suggestions it would be greatly appreciated.

I have resolved the issue with the surround sound, and yes it was the wires. But I still cannot use my headset in the front mic jack, but strangely enough the front output jack works fine. I'm pretty sure the motherboard is at fault here. As I know another person with the same problem. Any ideas?

^^^ most likely, however there are occasionally motherboards that have jumpers or bios settings enabling dp audio sockets. Have a flick through your motherboard manual and see what it says about the fp audio headers and if there are any jumpers you need to set to enable the line in. Worth a try if all else fails.