In order to hard reset a O2 XDA Stealth, 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 Stealth device will be brought back to the default configuration of a brand new device.
1. Switch off the phone.
2. Press and hold the Windows + Power + Ok buttons.
3. Device will now reset and restart, which will take a few minutes. That is all.