This is only a hunch, but because you bought it second hand it might not be a PS2 from your country.
It might really be a JAP/AUS/US or EURO PS2 (there are four different numbers for the four different regions, what number is yours?).
I know that there are some chips that will allow you to play PS2 games direct boot, but not PS1. This could be your problem. I would find out from the original owner, and send it back, only cause piracy is illegal and won\'t get you very far.