What's your problem?the game could not be started [80020321]

This error is appearing because there is a setting in the hidden configuration menu that is set to require a UMD game disc to be in the PSP when it attempts to load.

Turn off the PSP, then hold the R button down while turning on the system. You will be in the Recovery mode/Configuration menu. Choose configuration, then go to the 5th option, and press X once. This will switch it to "NO UMD". Then press X on "Back", then "Exit". Once you restart you should be able to load the ISOs, CSOs etc. without getting the 80020321 error.

Hope this helps you!