downloading psp games, totally stressed, help

[babbles]

My nephew has been wanting a psp memory card for ages so he could download games.
I finally bought him one and my stress levels are now through the roof
I have downloaded some psp games from torrent sites.
I plug in his psp..usb mode..and a folder appears with music, games etc listed in seperate folders.
In the games folder I create a new folder and call it after the game.
I then open the torrents download of the game and drag all the files in it to the newly created folder.
You can then see they are transferring to the psp.
However every one of them is coming up as corrupted data on the psp.
Can anyone tell me what I am doing wrong, or point me in the direction of a psp for dummy aunts walkthrough.
Thanks in advance