How to play cso file on psp?

I downloaded a cso file and i transfered it to psp but i am not able to play. wat can i do? (firmware 5.03)?

• i hav a psp of firmware 5.03. i downloaded one cso file from mininova and i transfer it to my psp by creating a ISO folder.. but wen i go to games on psp it says no files.. so pls tell me how to play these games.. i read about the concept of downgrading the psp? y is it so? pls let me a solution to play these cso & iso files on my psp.

• Answer:

  All of your steps above are corrent but yes you must downgrade unfortunetily the only way u can do that is by pandoras battery and knowing you didnt know exactly what downgradeing is you will run into afew problems u may hav to know a friend with a hacked psp that can do it buy pandora batterys magic mem stick off ebay or yake to a shop that will do it for but they usually overcharge it cause it could be done in 5 mins if you know what your doing good luck anyway