If you need to do a factory reset on the Chromecast device on the first and second generation Chromecasts.
Step 1: You will need to pull out the device from the TV’s HDMI port
Step 2: Once you have Chromecast in-hand press the small button on the side of the device for about eight seconds. The Chromecast’s indicator light will blink while you’re holding the button slowly first, then faster once it gets closer to resetting. After the light goes solid, you can let go of the button.
First Generation model
Second Generation model
Now your Chromecast has been reset!