In order to hard reset a O2 XDA Star, 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 Star device will be brought back to the default configuration of a brand new device.
1. First, use Power button to turn off the phone.
2. Now press and hold these buttons: Power + Call + End.
3. Follow the on-screen instructions. That is all.