1. Soft Reset/Normal Reset: With this method, the mobile setting are restored to factory settings. But it does not remove applications, games or anything installed. To do this reset press *#7780#.

2. Deep Reset: It is the most common way to reset your mobile. It will erase all the bugs and errors in your phone including all installed applications and games on your phone memory. *#7370#

3. Hard Reset/Format: If due to any problem you are not able to go to the screen of your mobile to enter the above mentioned codes, then you will have to do the hard reset or to format it. Symbian S60v3 and S60v5 mobiles have different method for reset but N97 and 5800 have different.

a. To reset the mobiles other than N97 and 5800, keep pressed the following three keys on your mobile keypad and restart your phone while still pressed these keys. * + 3 + Call button (green button).

b. For Nokia 5800 XM: In this case, press the keys at once Red (End) + Green (call) + Photocamera Button and hold and switch on the mobile.

c. For Nokia N97: Press both Shift keys + space bar and BackShift, hold, turn on the phone.

Note : All data will be lost during this process, so back up all your data before you go for these procedures.

Read more: http://howtodoarticles.blogspot.com/2010/0...l#ixzz11V4bBFBq