I was utilizing a new USB headphone/microphone set instead of my normal devices which plug into the jacks on the side of the computer.  Everything worked great when the computer detected the new USB audio device and installed the driver.  Unfortunately, when I was done with the USB device and attempted to connect the old set of headphones, the computer would not detect them.

Upon further investigation, the computer told me there was no audio jack installed on the computer at all!  Evidently the USB device driver had disabled the audio jack completely to where it could not even be detected.  To regain sound, I had to uninstall the USB audio device driver.  This allowed me to access my audio jack settings again.

Beware of what certain device drivers can do!