1. The most common issue when faced with a non-working keyboard is an improper connection. Try to reconnect your keyboard, restart your computer and verify if that fixes it.
2. Turn off the system. Unplug the keyboard connected and check for any bent or broken pins. If the pins are bent, it's possible to gently straighten them thanks to the tip of a ball point pen or mechanical pencil. If the pins are broken, then a replacement of the keyboard might be necessary.
3. Try updating the device driver. Visit the manufacturer's site for the latest drivers available for your keyboard maker and model.
4. While at the manufactures web site. See if there are software updates available for your keyboard. If there are any, go ahead and install them as well as the updated driver.
5. If you are using a multimedia type keyboard, be sure to remove the software before installing any new drivers for this type of keyboard.
Install the updated driver provided by the manufactures website, then re-install the keyboard software. If any software updates are available for your multi-media keyboard, install them at this time. Remove the keyboard software by using Add/Remove Programs (Start>> Control Panel>> Add/Remove Programs). If you receive an alert asking if you would like to remove all shared files, answer "No to all". Then click OK.