In order to hard reset a Sony Ericsson P990, 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 P990 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. Confirm the process and follow the on-screen instructions.
4. Phone will now reboot and restart. Done!