Menu-->Settings-->Restore Factory Settings-->All..
I am sure you know that in absense of a back-up you will lose all your data thru' this process...
2012-04-19 19:52 - edited 2012-04-19 19:53
As answered by Farby, if you follow these steps, your phone will be completely formatted.
The process will (clean) re-install the current software version in your C3.
You can always choose to (re)install the latest update using Nokia Suite on your PC via USB.
All the best,
Use the latest version of Nokia_Suite ... Once installed connect the phone to PC thru' USB and open Nokia Suite -->Tools-->Software Updates..