5.1 Surround issue, brand spanking new system

Hello everybody,
I'm posting this evening in hopes I can get some help with a problem I've been having with my surround sound speakers.
I have a set of Altec Lansing speakers, which have worked flawlessly in the past (on a Windows 7 system I might add). I recently purchased a new computer system and now I only seem to be getting sound out of my 2 front speakers all the time, and sound from my sub only when I have my speakers set to "Ster/Surr" and not when set to "5.1 in". When I use the Realtek HD Audio manager AND the built in Windows sound components to test the speakers, they all work perfectly, and I can get the testing sound to play from each of my 5 speakers and my sub. Any games, movies, videos, music etc. I listen to however only plays in stereo.

Here is some additional information that may ease the process:
Mobo: ASUS P8H67-M Pro
Realtek HD Audio Driver Version: 6.0.1.6438
Audio Controller: HD Audio
Audio Codec: ALC892

Things I have already tried (to no avail):
-Reinstalling drivers
-Reassigning audio jacks (although as I mentioned above, the speakers DO work, they are just not receiving input for some reason)
-Downloaded the newest version of the Realtek HD Audio Manager
-Toggled and untoggled basically every audio setting I can find in Windows

As I mentioned above, I've had these speakers working on a Windows 7 system before, and I would very much appreciate any help that can be offered towards getting them to work on this system as well! Thanks in advance!

-Colin

Edit: With my last install of the Realtek driver, the HD Audio Manager seems to have disappeared from my computer?

Try unplugging all your jacks. Restart your PC.
Plug one in at a time, going through the jack detection process.
Do this for each jack you have.

What happens when you go to Environment and select Room?

No problem!
I'm glad it worked out for you. :)