Whelp, I really did it this time.
On my new work computer I didn't like the sound quality so was looking to improve it. I went into the Sound settings from the Control Panel, double clicked on the Speakers/Headphones to bring up the properties, clicked on the Advanced tab, and under the default format noted that it wasn't at the highest setting [24-bit, 192000 Hz (Studio Quality)]. That seemed like it might improve things so I changed it and hit apply. It locked up and never let go and eventually crashed. After that, no more sound.
Of course, I tried going back and restoring the default settings but no joy. Every time I try I get the error Format not supported by the device. I tried every single setting in there and they all return the same error. I've done multiple restarts, performed system restore twice, reinstalled the Realtek High Definition Audio drivers, restarted the Windows Audio and Windows Audio Endpoint Builder services, and even tried editing the registry to remove Default Launch Permission (found that as a suggestion on two different Google searches).
I'm pretty much out of ideas. Anyone have something else I can try?
Dell Latitude E5540
Windows 7 Professional 64-bit