There are two methods allowing you to reset your phone to a more unwavering state.
Normal Reset
Using the *#7780# sequence.
It will restore ini files from ROM keeping all your data (themes, 3rd party applications, video, photos, and music files)
Deep Reset
Using the *#7370# sequence.
Completely format phone memory. Default files are cleaned up and rewritten.
Note that data found on memory card will not be altered
How to proceed
When using symbian60 v1 based phone such as nokia 7650, 3650 or N gage models these two key sequences can be entered in the same way you dial up a phone number. The phone will prompt you to enter a security code (12345 by default).
On the latest S60 phones you can try a Deep Reset, using the following steps
Turns off the phone
Press simultaneously on the green/talk, 3 and* keys and hold the 3 keys.
Turn on your phone
Wait for the onscreen Format message then can release the three keys
This method may also work for Nokia phones that won't turn on.
Note that before making a reset on Nokia's latest phone (N96),using the *#7370# or the 3 finger method, better make a backup, as you will automatically delete important data:
The license for pre-loaded contents (music, video, maps,etc..) and pre-installed application (N-gage).
Better use this method (reset) as a last resort.
