Thanks, I was having a similar problem and this totally solved it. Thanks!!
After 2 days of relentless troubleshooting I have found my solution to this very annoying problem. The problem being a 5.1 speaker setup is functioning only as a 2.1 system. More specifically only the front, and sub are capable of playing audio. The remainder are dead silent unless tested with either windows speaker configuration or Realtek audio manager tests in which case ALL your speakers WILL produce sound.
If you are experiencing this problem, and have exhausted all suggestions online as I had just done today, here is one last thing you could try (extremely simple and for some reason not available anywhere else online) so here is my contribution, since I could not fathom another human being experiencing such frustration as I have over such a thing.
Assuming all the basic things such as the audio driver have been installed or updated, and the correct playback device has been selected etc.. (All which are available in countless other posts online) then try the following...
1) open control panel > click on Realtek HD Audio Manger
2) under speaker configuration just verify 5.1 speaker configuration has been selected
(note that the "center" , "subwoofer", and "rear pair" boxes should be automatically selected under the "optional speaker" title AND the "front left and right" box should be selected under the "full range speaker" title)
3)IMPORTANT**** Deselect the "front left and right" box under the "full range speakers" heading
4)IMPORTANT***** Go to the "DTS CONNECT" tab and click it to "on"
THATS IT! yes I know its that simple....
the combination of deselecting the "front left and right" box and enabling "dts connect" is the magic to all this..
I hope this worked for you as well. Cheers!