If the device has frozen, or some of the facilities have stopped working, this can mostly be solved by power cycling, or resetting, the device. To do this, follow the steps below:
1. Push and hold the Power On/Off key.
2. The screen will now show Power Off/Reboot. Ignore this, and carry on holding the button.
3. After 15 seconds the device will be restarted.
If the device has a battery that can be removed, then you can also achieve the same effect by doing that.