How can I disable the caps lock key? Is there any way to completely disable the caps lock key without using any third-party apps?

(Virtually, of course—I don't plan on jamming something under the key.)
Just use the Keyboard pane of System Preferences.

Click "Modifier Keys", and set "Caps Lock" to "No Action".


  

n.b. This setting can be different if you have more than one keyboard.