How to reset Airport Express Base Station
If you own an Apple AirPort Express station, here's a guide on how to restart and reset your base station & configuration:
With the AirPort Express plugged into a power outlet, launch the Network System preference and choose AirPort from the Show pop-up menu. Click the TCP/IP tab and choose Using DHCP from the Configure pop-up menu. Press and hold the device's reset button for 1 second. The light will flash yellow and you'll have five minutes to make changes before the AirPort Express reverts to its previously saved configuration.
With the AirPort Express plugged into power, press and hold the device's reset button for 10 seconds. A green light will flash for a bit and then the device will reset itself — a process that takes about 45 seconds. Once reset, you can configure it with the AirPort Express Assistant or the AirPort Admin Utility.
Unplug the AirPort Express from the power outlet and press and hold the reset button. While still holding down the reset button, plug the device into a power outlet. Hold down the reset button until you see the light flash green four times. Let go of the button and the device will reset itself. Wait the requisite 45 seconds and configure it with the AirPort Express Assistant or AirPort Admin Utility.