In the Sounds and Audio Devices control panel, under Speaker settings >
Advanced, Windows allows you to "select the speaker setup that is most like
the setup on your computer". I've seen various recommendations to set it to
"Desktop stereo speakers" even when using headphones.
What do these settings do? What does the Headphones setting do? As near as
I can tell, there is some EQing, but it must be more than that, since some
people complain that surround sound doesn't work right if they haven't picked
the right speaker setup. I suspect there is some mucking about with the
stereo image. Anyone know?