Great answers all around, but I think I found the shortest answer yet:

• Open Device Manager.
• Scroll to: Sound, video and game controllers.
• Locate: IDT High Definition Audio CODEC. (Surprisingly, no, the problem is not located under Audio.)
• Right click and click uninstall. Reboot. Your machine may re-add it, but it should be properly configured then.

Great answers all around, but I think I found the shortest answer yet:

• Open Device Manager.
• Scroll to: Sound, video and game controllers.
• Locate: IDT High Definition Audio CODEC. (Surprisingly, no, the problem is not located under Audio.)
• Right click and click uninstall. Reboot. Your machine may re-add it, but it should be properly configured then.

The above solution worked until you reboot. In the end, I had to do a fresh OS install. I recommend finding a more modern, up to date OS to install from scratch.