as tolien said, you will need to reset the router - look at the back of it for a small button (you may need a pencil to push it), turn the router on and press the button for 5 to 10 seconds until you see the lights on the router flash or go out - once its reset (may take a minute) the default user name and password will be required to access it (try admin/admin, admin/password, or check your documentation).