In order to hard reset a Sony Ericsson W205, 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 W205 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 either Reset All or Reset Settings.
4. Done, the phone should now reset'n'restart.