You need to just get a program called UMDGen. It’s free and works on Windows.
Then you download the template.dat file that Reeshmd23 posted on the previous page and extract the zip file and get the template.dat file out.
Open up the Madden 08 psp ISO file using UMDGen.
Drag the Template.dat file and replace the one in the DATA folder in UMDGen. It’s a couple folders in from the main folder in the UMD explorer window. Don’t have it available right now to give you the exact location.
Then Save the new UMD ISO as madden08mod or whatever you want to call it. Then you can transfer your game to your CFW PSP/Vita or play it on the ppsspp.