If you have forgotten the router's user name and password, and the default user name and password aren't working, try resetting the router back to factory defaults:
With the router powered on, hold the reset button (located on the back of the router) for 25 seconds. Then disconnect the power from the router and wait 10 seconds before plugging it back in.
After the reset, you should be able to login to the router with the default user name and password.
