Do you have a USB keyboard?
If so you have to enable USB devices in your BIOS, you need to boot and interrupt the boot by pressing the delete or esc key (depends on your Mother board). Once you get into the BIOS you need to find the bit that covers USB devices, possibly Integrated Devices or Peripherals, but this again depends on maker of the BIOS chip. You will have to search around for it and enable USB on boot.