Downgrade/removal of M33 VSH

[KriptiKFate]

My issue here is this, bought a PSP with custom firmware for the gf, she doesnt understand how to use it, need to remove it and go back to any .ver of official Sony firmware.

Details:
I have an old PSP1000
My current version is 3.71.
Older official versions either tell me that my system configuration is not correct and the update cannot be completed, or that my version is newer than what I'm trying to install and won't let me.

If someone could explain to me in detail how, if possible, I go back to official Sony firmware I would very much appreciate it, or - if you could explain to me what settings I need to use to run Official UMD's with M33 VSH, that would be great too, I've tried every UMD ISO Mode and none of them will run Ratchet and Clank, but the seller I purchased it from assured me he had just played it and it ran fine.

Thank you all in advance for your time and help.

[BCman]

firmware isnt likely the problem.
id say the umd is scratched or ruined in some way or the UMD drive is broken.

whatd i do if i was u is upgrade to 5.00M33-6 and play all the games directly off the memcard.

All M33 firmware is is a copy of the official sony firmware with some tweaks that allow the psp to be used at its full potential.