cfw uninstalled need help

hi all my psp was running 3.80 m33-5 and the kids got ahold of it and it is now just a normal version firmware no longer custom firmware i think they put a umd in and updated the firmware from the umd thats the only thing i can think of that they could have done
anyways how do i get my psp back to cfw will i need a pandora battery or soft/hard mod my battery etc...
or not because its already had cfw on it ?? can anyone give me a hint in the right direction
if it helps the firmware on it now is system software version 4.05
thanks in advance

Yes, you will need to use pandora =/. There are a few tutorials on the Tutorial section that will show you how to make it.

cheers thanks for that ill make a pandora by using this can i just go straight to the firmware i want and is the 5.0 m33-4 good?
so if i make a pandora and a magic memory stick with the firware i want is there anything else i need to get the firmware on the psp its a slim by the way
thanks

from what i gather when i install the firmware from magik mem then i update to the firmware i want to use is that right ?
thanks

Yes, if you set up the magic memory stick right, you should have at least one high firmware eboot file like 4.00 on your stick, so you can upgrade to the 4.00 Custom Firmware.