In order to hard reset a Sony Ericsson W710, 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 W710 device will be brought back to the default configuration of a brand new device.
1. Turn on the phone.
2. Select Menu > Settings > General > Master Reset.
3. Now select Delete all user installed applications and Delete. Confirm.
4. Tap in your phone's lock code and select Done.