Today we will explain how to set the lock code of our Nokia N97 or N97 Mini. Something simple and useful, to make life harder for thieves.
Steps:
In this way so simple, every time we turn on our Nokia will ask the lock code. In addition, it is good change the default code, so, if we have blocked our Nokia remotely via SMS, the thief do not have so easy.
And now we will activate the Phone autolock period, for this
We can also activate Lock if SIM card changed in Menu > Settings > Phone > Phone mgmt. > Security > Phone and SIM card, so it will be harder for the thief 
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i forgot my lock code and i want to change it.
i forgot my lock code and i want to change it.
my cell phone tells me (code error) please help me!
i forgot my lock code and i want to change it.
i forgot my lock code and i want to change it.
I am facing the same problem.
i want to know that how can i put a password that no one can open my phone. phone lock is only while starting. but is there anything for nokia n97 that we can put password every time we unlock the phone.