Hard Reset HTC Desire

1. Turn off the phone, remove the battery and insert the battery again.
   
2. Press and hold the VOLUME DOWN button, and then press and hold the POWER button.
   
3. Wait for the screen with menu.
4. Press the VOLUME DOWN button to select Clear Storage and then press the POWER button.

WARNING !
Hard Reset will erase all of your data
All described operations you are doing at your own risk.