OK just got my Daughter a new PSP 3000 09g

I installed 6.39 LME-8 and changed the settings in video when you hit select button but every ISO i put on my psp iso directory says it's corrupt.

Not sure what I'm doing wrong is there a better customer firmware that is easy and will work with all games.

I bought 9 games and I will also be dumping these so my daughter doesn't ruin them.

Thank in advance for the help being offered here.