|You are going to have to reset the router to factory defaults and then use the user name and password that the router came with.|
You can do this by pressing a straightened safety pin in the little hole in the back, usually marked "reset" and holding it for a bout ten seconds. Do this with the power applied.
You will then need to reconfigure the settings in the router. The default user name on a Lynksys is usually blank with the password being admin. You need to check your manual because there are variations.