Interesting this topic. I have a SoundBlaster Live 5.1 SE, had the normal two speakers and last week I bought a set of new speakers with the subwooker etc, set the soundcard up through the soundblaster panel for 5.1 sound, but when I run test it doesn't speak through the centre/subwooker speaker.
And when good old reliable XP Pro with SP1 crashes and reboots, I am back to two speakers.