HAVING an iso or .cso isn't as illegal as everybody thinks it is. It is possible to extract the contents of the UMD yourself and make your own image. Same reason people use no-cd cracks and all that, so they keep their original media in good shape. Plus using an image on the memory stick of the psp helps load times and increases batt life since there's no laser on and no disc spinning. Just because somebody is using a .cso doesn't mean they don't have the game.