Liquidzigong has a nice Christmas gift for you. He has released a Prometheus ISO Loader for 6.20 TN-A (HEN). All you need to do then is just create an ISO directory in the root of your memory stick or intenal memory on the PSP Go. And then move your legally backed up ISO’s to this folder
Download and extract the Prometheus ISO Loader contence to PSP/GAME and then Start 6.20 TN (HEN)
If you want to use the M33 driver, you need a copy of 5.00_isofs.prx which is not included in this package. You can get this file from the official firmware, by using PSARDumper and PSP Firmware 5.00 here