Apple iPhone hard reset
If iPhone won’t turn on, or if the display freezes or doesn’t respond
* Press and hold the Home button below the screen for at least six seconds, until the application you were using quits.
* If that doesn’t work, turn iPhone off and turn it on again. Press and hold the Sleep/ Wake button on top of iPhone for a few seconds until a red slider appears, and then drag the slider. Then press and hold the Sleep/Wake button until the Apple logo appears.
* If that doesn’t work, reset iPhone. Press and hold both the Sleep/Wake button and the Home button for at least ten seconds, until the Apple logo appears.