In order to hard reset a Sony Ericsson D750, 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 D750 device will be brought back to the default configuration of a brand new device.
1. Install PC Suite. Download it from the official Sony website.
2. Handset must be turned on to perform this operation.
3. Start the application and plug your phone to the PC.
4. Open Tools and Phone repair. Select your phone model.
5. Continue with the installation.
6. Allow the phone to reset'n'restart. Done.