NokiaLumia 800 / Lumia 900Mobile phoneResetting to factory settings
Important: Resetting the mobile phone will delete all saved data and settings. Some problems may be resolved by simply restarting the telephone. Another possible solution is to install a Software-Update.
Recommended: Save your data using Zune, before resetting your Nokia Lumia 800.
The following steps contain instructions on how to reset your Nokia Lumia 800.
Go to the Start screen.
Scroll to the right.
Choose reset your phone.
Your Nokia Lumia 800 is reset to factory settings. The mobile phone will reboot.