The model would be handy to know?
You could try a hardware reset, whether that'll clear the password I don't know. The reset procedure seems to be pretty generic for speedtouch routers
1 Make sure the SpeedTouch™ is powered on.
2 Power off the SpeedTouch™ by pressing the power button until all LEDs turn off.
3 Press the power button once again (shortly).
4 As soon as the Power/System LED is flashing green, press the power button once
5 The Power/System LED stops flashing to become solid green. After six seconds, it
starts flashing green again. Press the power button once more (shortly).
6 All LEDs flash green once.
7 The SpeedTouch™ reboots and will come online with factory default settings.