In order to hard reset a Nokia 8910i, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia 8910i device will be brought back to the default configuration of a brand new device.
1. First, press and hold the Power button to turn on the phone.
2. Press the Call button and tap in the "secret" code *#7370#, confirm.