Once you install the custom firmware on your PSP, you wont be able to play the games from backup ISO/CSO files. This needs to be enabled in the M33 menu. To do this peformt the following:
1. Click on the ‘Select’ button for 2 seconds. A translucent menu would appear. This is called the “VSH Menu”
2. Navigate to ‘UMD DEVICE’ and select “Memory Stick”
3. Navigate to ‘UMD ISO MODE’ and select SONY NP9660 or M33 Driver
4. Exit then menu
Now you should be able to play games from ISO/CSO files
Thisworks only on PSP’s which are installed with M33 custom firmwares
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