Greetings,

It has been long since I've played with my PSP Fat, the original PSP-1000 since my battery went kaput. Now, I've bought myself a new battery for it.
But, it's still running on a dated custom firmware which is 3.71 M33-4. Can someone please guide me on how to upgrade it to the latest custom firmware?
I believe I can't straight update it to the 5.50 custom firmware, or can I?

Thanks.