I have Logitech Z5500 speakers (5.1) running on a Soundblaster X-Fi Titanium soundcard.
Both the Creative software and Windows's audio options think that my speakers are only 2-channel "stereo" speakers.
I figured it was the cable going from my speakers to my soundcard, but I have replaced that and it didn't fix the problem. Where do I go in Windows 7 to tell it that it should be outputting audio on 6 channels (5.1) instead of 2?
Resolved. It turns out I was looking in the correct place (Control Panel > Sound > Playback tab > click "speakers" > hit Configure button); but Creative's drivers were messed up (what's new, right?) and that was causing "Stereo" to be the only speaker configuration available for me to select.
The solution to the driver issue was to not only update the drivers, but first completely uninstall/remove every single piece of Creative and/or X-fi related software from my system, then reboot & install the newest versions of everything.
If Creative actually had some competition in the soundcard market, they would have gone bankrupt by now due to their complete inability to program working drivers for their products. Seriously, Creative must have some incredibly incompetent people working for them - it seems like every time I hear anyone mention Creative, it's something about a malfunctioning feature, instability, or lack of driver support.