I bought new speakers, which caused one of my computer's sound drivers to fail. Troubleshooting told me to uninstall it, and then reinstall it. After I uninstalled it, my computer restarted itself, and then I had sound. I have no idea how or why this course of events unfolded, but it did.
Now if I hadn't lost all of my mp3 files of dubious origin, I'd have something to listen to.