This is NOT a tutorial on how to make Sims 2 poseboxes in general! It is a tutorial on how to clone poseboxes correctly!
If you want to learn how to make poses and poseboxes, there’s a great one by Digital Angels here.
Just as it is possible to make a base-game compatible object even if you have all Sims 2 EPs and SPs installed, it is possible to make a base-game compatible posebox even if you have all EPs and SPs installed. To do this, you need to change some settings in SimPE (just as when you make objects) – before you clone your posebox.
Note that this will NOT affect any poseboxes you already have in your game! The SimPE settings have to be changed before the posebox is created to have any effect, so if the posebox in question wasn’t cloned properly to begin with, there is nothing to be done.