--While using your mobile pones sometimes you may get some problem in its functioning like the camera not working, virus infected like commwarior, OS works very slow, bluetooth not working, in that case the first and foremost step is restore your original factory settings. Here I’m telling you how to track back the original settings and if the problem still persists than there’s an alternative approach for doing so.
Resetting Phone factory settings by Nokia secret codes.
This method is very simple one and you don't have to do much effort. In this process factory settings are restored i.e. phone is switched back to default settings and no application is deleted.

First Method
Before you start this first backup your phone books, calender and any other important stuff to your PC or memory card and then simply enter this code
*#7780#
It will ask for “Restore all phone settings-phone will restart….”
Then it will ask for security code, enter your security code whose default value is 12345 and then the phone is reset after restart. After doing all this phone will be restored to the time when you purchased the phone and no application is removed.

Second Method
The other method is formatting memory disk. It format the phone memory, everything that has been installed other than the default applications that were present at the time of purchase will be deleted. The phone restored to time to you purchased keeping the original software intact.
Just enter the code:
-#7370#
Then it asks for security code, enter your security code and by default its value is 12345 and process as done in previous method.
Before starting just take backup of all the necessary data like contacts, calender etc.
Note : Battery should be fully charged or be connected to charger so that it may not run out of power.