I am having the same problem. I had all my speakers working but when I updated my realtek drivers for some reason I cannot get the woofer and rear speakers working again. Tried rolling back the driver and it did not work. Now I forgot what I had to do to get all speakers working
I'm using WinXP and a Gigabyte MB, GA-EP45C-UD3R with a Realtek ALC889A codec.
Any suggestions?