In order to hard reset a Nokia 6800, you should perform the following steps.
Remember! Hard reset will delete all the data on your device; pictures, contacts, messages, apps and more.
Nokia 6800 device will be brought back to the default configuration of a brand new device.
1. Turn on the phone.
2. Open Menu and Settings and choose Restore Factory Settings.
3. Type in the phone's security code - 12345 by default.
4. Voila, done.