This is Custom Firmware 5.50 Prometheus for your PSP running on any lower version of CFW that was Prometheus. This enables us to play more of the newer games and also gets rid of some of the glitches. Just Extract the files and put the 5.50_PRometheus4 folder in the PSP folder and run the installer and your done.
Note: May not be the first on your Game List!!!
Also need to be on CFW 5.50 Prometheus to install or GEN D3 FIX