Hy, my OS is XP and I have Inspire 4400 4.1 speaker. Everything is OK on the panel, I can hear the sound from all speakers on test but in games there is no sound from the front left and right rear speaker. I tried every jack, 2CH speaker mod etc, uninstall AMD HD Audio Device. Nothing works. I noticed that it worked suddenly for a short time but now it doesn't. I really don't know what is going on. Any help will be much appreciated.
I had a similar problem with 5.1 speakers. I solved it by plugging each of the cables in one by one and waiting for the RealtekHD popup on the screen asking which channel you have just plugged in, and then selecting the correct one.
You may or may not be having the same problem as me but give it a try. Disconnect all speakers and do one by one cable.