A reset to factory settings should be used only as a last resort when troubleshooting. All personal data, files, settings and installed apps will be removed and cannot be recovered.
Also, please note that in order to connect your controller or remote after a factory reset, the on-screen instructions will not be valid. Instead, follow these instructions: http://shield.nvidia.com/connect.
NOTE By performing a factory data reset, all data will be wiped from your SHIELD. Data associated with your Google account can be recovered. Any device settings will also be removed.
NOTE For the SHIELD Pro model, full reset will take up to 2 hours. All personal data will be erased from the 500 GB hard drive. You will also have the options to perform a fast reset.
To reset your SHIELD to factory settings, follow these steps:
From the Home screen, scroll down and select Settings .
Under "Device," find and select Storage & reset .
Select Factory data reset.
Then select Fast Reset or Full Reset depending on your preference.
Then select Erase everything to confirm and reset your device.
To access the fastboot menu:
Turn off your SHIELD.
Unplug the power cable from your SHIELD..
Connect your SHIELD to your PC/Mac/Linux machine's micro USB port.
Plug the power cable back into your SHIELD.
Wait 2 seconds, and then hold the NVIDIA button for 5-6 seconds until you see the fastboot menu on the display.
After you reset your SHIELD to factory settings, you need to reinstall any apps or games.
Go to the Google Play Store app .
Find the app or game, and select it.
In the window that opens, select Install.