I believe Realtek onboard has some problems with Skyrim. Do you get surround sound support in other games?
You can either wait for a Skyrim patch from Bethesda or Realtek, or buy a Xonar DG soundcard on the cheap (£20) or go a bit upmarket and get a Xonar DX.
Do you use headphones or speakers? I'm pretty sure for headphones you need to use Dolby headphone. I'd imagine it should be a default in games in the audio options.
I know in DA:II you get to force stereo mode, so 5.1 is by default. I'd think it the same for many games. Have you got the latest realtek HD audio drivers? I have the same mobo as you but I dont use 5.1 yet. I asked my wife for a pair of the Corsair HS1 surround headphones for Christmas but that uses USB.
On the contrary, you only need to enable DS3D GX mode on an ASUS Xonar card, I think the same 'Game' mode applies for Creative - Enabling EAX? That's what delivers the positional cues
The only feature that Dolby Headphone adds is reverb, to make it sound more 'life-like'.
The feature
really annoyed me when I was playing Saints Row 3, everyone sounded like they were standing in a studio, talking to me through multi-directional speakers via a microphone. Quite literally, it sounded like they were standing in the middle of an echoey room.