mantukis5000 :
Buy usb to ps/2 adapter for your keyboard if your motherboard has one free ps/2 port.
What this guys said. If you're connecting a USB keyboard on an older motherboard sometimes it won't automattically recognize it.
Look for or buy and old Keyboard/Mouse with a PS/2 port. Can usually be found for under $10 in old PC stores. Should fix the problem.