In order to hard reset a Sony Ericsson J100, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Sony Ericsson J100 device will be brought back to the default configuration of a brand new device.
1. Turn on your PC, open Sony's official website and download and install the PC suite program.
2. Turn on your phone, start the app and plug the phone to the PC.
3. Open Tools and select Phone Repair. When there, select the model of your phone.
4. Complete the installation process. Wait for the phone to reset and restart. Voila!