Nokia mobile secret codes:

On the main screen type
 
*#06# for checking the IMEI (International Mobile Equipment Identity). 
 
*#7780# reset to factory settings.
 
*#67705646# This will clear the LCD display (operator logo).
 
*#0000# To view software version.
 
*#2820# Bluetooth device address.
 
*#746025625# Sim clock allowed status.
 
*#62209526# - Display the MAC address of the WLAN 
 
adapter. This is available only in the newer devices that  
 
support WLAN 
 
#pw+1234567890+1# Shows if sim have restrictions.

*#92702689# - takes you to a secret menu where you  
 
may find some of the information below:
 
1. Displays Serial Number. 
 
2. Displays the Month and Year of Manufacture
 
3. Displays (if there) the date where the phone was   
purchased (MMYY) 

4. Displays the date of the last repair - if found (0000) 
 
5. Shows life timer of phone (time passes since last start) 
 
*#3370# - Enhanced Full Rate  Codec (EFR) activation.  
 
Increase signal strength, better signal reception. It also  
 
help if u want to use GPRS and the service is not  
 
responding or too slow. Phone battery will drain faster 
 
though.
 
*#3370* - (EFR) deactivation. Phone will automatically  
 
restart. Increase battery life by 30% because phone  
 
receives less signal from network. 
 
*#4720# - Half Rate Codec activation.
 
*#4720* - Half Rate Codec deactivation. The phone will  

automatically restart
 
If you forgot wallet code for Nokia S60 phone, use this 
 
code reset: *#7370925538#
 
Note, your data in the wallet will be erased. Phone will ask  
 
you the lock code. Default lock code is: 12345 
 
Press *#3925538# to delete the contents and code of 
 
wallet.