In order to hard reset a BenQ-Siemens P51, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
BenQ-Siemens P51 device will be brought back to the default configuration of a brand new device.
1. First, locate the Reset button at the bottom of the device.
2. Now some dexterity will be required - press and hold Power button and, as you hold it down, press the Stylus (pen-thing) against the Reset button.
3. Keep holding those two buttons until the screen fades. Done, the hard reset operation is complete.