Please follow this instruction you also can watch the video
1. Turn the Desire S off. If it’s frozen on, take the battery out and put it back in the unit.
Now to wipe the device clean:
3. Navigate to the clear storage and press the power keys to confirm the selection.
4. That should bring you to a sub menu that need you to confirm the clear storage option
5. Confirm the clear storage action by pushing the volume up keys
The device should then reset again and the hard reset is complete.
NOTICE
hard resetting your phone/pda will bring the phone back to factory setting. Make sure to save the data you want before doing a hard reset because you will lose all content on the unit.
Please do this with your own risk!.