some ISO's dont work

Hey guys, some of the ISO games don't work on my custom firmware, particularly rachet and clank and guilty gear, the file is ISO, but when i put them in my mem card i dont see them in the game section, does anyone know of similiar problems or how to solve this?

are you putting them in the iso folder

yea i am, the cso work just fine, the iso's dont for some reason

a bit strange did you download the games?

yea

they might be bad downloads...corrupt...convert them to cso and if they still dont work its just a bad file