My Nokia 7610 was brought from a friend of mine, and he forgot the lock code. I could have brought the phone to nokia service center for reset, but usually it takes few days, and it will cost me some money, because it is already past the warranty period. Luckily I found a program to retrieve the phone code for free.
UnlockMe! is a software that will allow you to recover the Unlock Code that is currently configured in your Symbian phone. You have to install and run the software on the phone, and it will try to brute force your lock code (it may take almost an hour depending on your lock code).
This is the kind of program that you only need once in a while, but very useful when you need it. You can download this program from: http://www.symbian-toys.com/unlockme.aspx.