|Did the keyboard come with a drivers disk? If so try to reinstall the driver. If not then got...|
Start -> Control Panel -> System -> Hardware Tab -> Device Manager button -> Scroll down to Keyboards, expand it -> Remove the HID Keyboard Device.
Then reboot your computer and it should detect your keyboard as a new device and install the Plug-And-Play drivers. You will need to give your computer about 30 seconds to install the driver after rebooting.