In order to hard reset a Sony Ericsson S710, 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 S710 device will be brought back to the default configuration of a brand new device.
1. Switch on the phone.
2. Go to Menu > Settings > General > Master Reset.
3. Select Delete all user installed applications > Delete. Confirm.
4. Tap in the phone's lock code. Done.