buy a new keyboard and replace it. ebay is full of them. some keyboards are easy to replace and you only have to undo a few screws and a cable. some are a pain in the butt and require taking apart half the laptop, 37 screws, all different sizes and lengths, ton's of small wires and cable and clips that break if you look at them too long.
Just depends on the laptop if it's a newbie proof install, or intermediate skilled.