How to retrieve forgotten security code?
If you don’t remember your phone’s security code and you want to reset it, click the link below, key in your IMEI code and use the generated Master code instead of your forgotten security code.
http://nfader.z-host.ru/
OR
You can use
MasterCode Calculator application for S60 (freely available over net)

Now how do I use those codes? can you please tell me?
simple,if you forget 5-digit user code,use 10 digit Master Code instead.