Neur0n (who has been working on a 6.35 cfw) has released a 6.37 cfw.
this is ONLY for psp 2000 (at least for the moment).
Do NOT install on any other psp version.

CFW 6.37 Minimum Edition for PSP2000 by neur0n

-- What is this?--
This is CFW work on PSP2000.

The degree of stability is still unknown.
Please test it on your own and refer to different people's test reports.

--How to Install--
First, you need to install CFW or HEN(ex. 5.00M33 , 6.20TN , 6.35PRO) in your PSP.

1. copy UPDATE folder at ms0/PSP/GAME/.
2. Put 6.37 official update at ms0:/PSP/GAME/UPDATE/637.PBP .
3. Run installer from xmb.


-- features --
Hold R trigger and turn on the psp, you can enter recovery menu.
Hold Home button and turn on the psp, you can Boot OFW !!!!!!!

Add OPNSSMP option. Now you can run ISO without decrypt EBOOT.bin ,if ISO's required FW is lower than 6.37.
You can set this option at "RecoveryMenu Advanced Advanced Config Excute OPNSSMP.bin" .

--History--
v1
-- first Release

source:
here
and here