You can restore factory settings in this setting. Be careful, however, since you lose all personalization and all data you have added on the phone.
Accidents may happen and your phone may stop responding. You can restore the original factory settings, but be careful, since this reset removes all data you have saved in the phone memory and all your personalization.
If you are disposing your phone, note that you are responsible of removing all private content.
You need to have the security code to restore the original settings. To reset your phone to its original settings and to remove all your data, on the home screen, type in *#7370#.