how do you get to parental code setup screen on ps2?

When we put a dvd in my sons ps2 it said the parental code was locked so I got the instructions how to reset parental code but now when we put a regular dvd in it keeps saying "no data" , but if I put a bootleg dvd in, it plays it.  So how do we get to the parental code setup screen and why is it saying no data for regular dvd's???