PS/2 Keyboard input not working, when plugged in num lock, caps lock, and scroll lock lights come on?

If it's the PS/2 port, there really isn't anything you can do besides replacing the motherboard since they are integrated together. If a USB keyboard works fine then just go with that. Also check to make sure that you are plugging they keyboard into the keyboard PS/2 port, plugging it into the mouse port will not work.