With the C6625 turned off, press VOLUME UP + 4 way pad UP + POWER ON. Password: 0000

Select Settings > Security > Reset: reset settings to their factory defaults

or

Use this method to hard reset your Samsung C6625 phone: Enter *2767*3855#. Warning! All your data including contacts, messages etc. will be lost! Copy all your necessary data/Contacts/Messages etc. to SIM or make backup to your PC before full reset! Take out SIM card before full reset.