A-ha! We are in the presence of a genius; I have sound again! Thank you, EEVIAC.
Although, if you'll allow me, I have another, much smaller, related problem that maybe you can put your intellect to. There are buttons on the front of my computer for controlling sound: volume up/down and mute. Before my re-installation of Windows, those buttons, when pressed, would bring up a quick, opaque box with a bar indicating volume level, which would quickly disappear after a second or two.
These buttons now still appear to control the sound, but I have no indicator. Do you--or anyone willing--know of how to get that back?