Capslock turns on intermittenly on Windows Login Screen

"My best guess is: there's random crud in your keyboard that's intermittently causing you to push the caps lock down when you push some other key, or is causing a short that's causing it to think the key was pressed. Or, you're accidentally hitting the caps lock key while you type.

I'd recommend swapping the keyboard and see if the problem recurs. If not, then it's a problem with your keyboard (or that evil coworker decided to give you a break)."