Belkin KVM STandard 9 pin mouse/keyboard to USB COnversion

You need to have the keyboard connecter (purple) connected to your computer in order for the KVM switch to recognize it. The computer is providing some power through the keyboard connector and this is what the KVM switch is feeding on.

If you have a USB keyboard, you may want to change your KVM for a USB compatible one. If you just want to use the KVM to switch your monitor, you may plug the keyboard (purple) connector of the KVM to your computer's keyboard PS/2 port and also connect you USB keyboard directly to your computer. It should work.