All Nokia phones  as well as almost all phones comes with the feature of locking its keypad to avoid accidental dialing. But it does not protect you from misuse in case the phone got stolen. To protect your phone in a more secure way, you can set up a security code to lock your keypad.

To set the security code, click Menu > Settings > Phone > Security keyguard. You'll be prompted for the Security code. By default this is 12345. Enter this and press OK. Select On and click Select to see the message 'Security keyguard activated'.

Now when you lock your phone you'll see the message 'Keypad locked with security code'.

When you next unlock you'll be prompted to enter the security code. Type your code and click OK to activate your keypad.

Changing the security code
Of course, if any potential phone thieves are reading this, they'll now know the default security code is 12345.

To change the security code, go to Menu > Settings > Security > Access codes > Change security code. When prompted, enter your current security code and click OK. The enter your new security code (a PIN between 5 and 10 digits in length), click OK and enter the new code again to verify it. Click OK and you'll see the message 'Security code changed'.