In order to hard reset a O2 XDA Nova, you should perform the following steps.

Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
O2 XDA Nova device will be brought back to the default configuration of a brand new device.


1. Press'n'hold the End and Call buttons. 

3. Pick up the Stylus and insert it into the Reset button hole.
 
4. Allow the phone to reset and restart, which may take a few minutes. Done.