Need help playing psx games on M33-5!

I only just recently installed M33-5 on my psp and have no prior knowledge of firmware, in other words this is my first time firmwaring my psp so i'm a newb.

I mainly got the M33-5 to play psx games and the first one i want to try is Tomba. I have the ISO for it and converted it using a GUI called "Another GUI Progamme". After that I put the eboot and .img files in the PSP/Games/psx games/tomba directory and go to play it in the memory card section of my games in my psp. But it says there is nothing in there.

Do I have to downgrade or something to get them working? Is there something I have to enable in the start up menu?
Please help as I have spent alot of money trying this and I don't want it to be a wasted effort...

If you are playing tomba the directory should look like this PSP/GAME/TOMBA , you just have an extra folder called psx games