In order to hard reset a Sony Ericsson Yendo, 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 Yendo device will be brought back to the default configuration of a brand new device.
1. Download the PC companion app from Sony Mobile's official website.
2. A window with four options should now open.
3. Hover over Support Zone Now! and select Start.
4. Wait until the installation completes. Afterwards, select Phone / Tablet Software Update and Start.
5. Continue by selecting repair my phone / tablet, accepting through every window that comes your way and preparing computer for software update.
6. Select the model of your phone.
7. Okay through and follow the on-screen instructions.
8. Connect your phone to the the PC.
9. Done.