This depends on your environment. Whatever program is directly talking to your keyboard is the place to start. If you are on Windows XP and have telneted into a Unix system, this could be a Windows XP problem. In the rare case of a tty being directly controlled by Unix, you would need to use the stty command. In the case of an X Server running on Unix it could be xmodmap or stty. But you want to track down why it is happening an undo that change. Don't simply introduce a compensating error with stty or xmodmap.