In order to hard reset a Sony Ericsson P910, 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 P910 device will be brought back to the default configuration of a brand new device.
1. Turn on your PC and download & install the PC suite Sony software.
2. In the meantime turn on your phone.
3. Start the PC suite app.
4. Now plug the phone into the PC. Then select Tools and Phone repair.
5. Follow the on-screen instructions.
6. Your phone should eventually reset & restart. Well done, stud.