Perform a Master Reset for the Sony Ericsson W300i
1. From the standby screen, press Menu.
2. Scroll to and select Settings.
3. Scroll to and select General.
4. Scroll to and select Master Reset.
5. Scroll to Reset Device: Clears all user-entered info, resets all settings, and deletes all configurations for MEdia Net access and e-mail. Phone will be restored to factory settings.
6. Screen will display "Phone will be restarted", press Continue.
7. If prompted to, enter the "Phone Lock Code" and press OK.
NOTE: The default lock code is 1111.