Nokia 105 has the hard reset option accessible from the menu option. In order to hard reset your device follow the procedure below.
1. Turn on your phone.
2. Go to Menu> Settings.
3. Go to "Restore Factory Settings".
4. On screen that demands the security code, type 12345.
5. Press ok.
This hard reset takes few seconds to a minute to wipe out any data on the internal memory. The phone resets it's configuration back to the factory settings.