I stupidly selected the "Update and Shut Down" option on a Wednesday morning, thinking that Microsoft couldn't be so inept to where it would clobber my settings so badly to where it would affect radio.
I was wrong.
Windows 10 did a major fucking update, to the point where it warned me it would "take awhile" upon reboot. Indeed, it took like 30 minutes.
Anyway, it came back on, and I found that my sound card's drivers were completely clobbered by the update, making them incompatible with the "new" Windows 10.
Among other things, there's no stereo mix anymore.
Now I have to grapple with this in the hours before radio.