Some noob terms to guide you all throughout.

ofw- Official Firmware

cfw- Custom Firmware

ms0 -root folder of your memory stick (what is root folder? google it :D)

homebrew - is a term that refers to home-made programming and software

m33 - cfw made by darkalex

mobo - mother board

What you need?

-PSP 1000 or 2000 (not for PSP 2000 w/ TA-088v3 mobo or PSP 3000)

-formatted memory stick

(Kindly download the following files)

-5.00 ofw

-5.03 ofw (if your fw is not yet 5.03 ofw)

-Your firmware should be 5.03 or less

-ChickHEN R2 - used to enable homebrew

-CFW Enabler 3.6

-HELLCATS recovery flasher 1.6 - used to permanently install cfw to your psp's flash

(Skip step 1 if you already have 5.03 ofw installed.) 

1. Extract the file (5.03 ofw if its in rar or zip file) then put the EBOOT.PBP in ms0:\PSP\GAME\UPDATE. If the UPDATE folder doesn't exist just create one.

Turn your psp on (I like this step heehee >:) then go to GAME. 

The 5.03 ofw update should appear from there, just run it and follow the update instructions.

2. Having 5.03 ofw installed. Use the ChickEN R2 (note that ChickHEN only works on 5.03 ofw)

Open the .tiff on PHOTO (slim.tiff for slim)

This should cause your psp to reboot. (if your psp crashes it meANS the process is not succesful, try formatting your memory stick)

Upon boot up, your fw should be changed to 5.03 M33 HEN

FAQ: Can I play ISO/CSO from this point? ANS: No, You can only run homebrews.

3. Now that you can run homebrew, run the CFW Enabler from GAME menu. This would change your fw to 5.03 M33-6 cfw

On this state you can play ISO/CSO from your memory stick.

note: This cfw resides only to your psp's ram and is not permanent, upon shutdown fw would be reverted back to 5.03 ofw 

and you have to go through the ChickHEN process again.

4. From this point, you can use the Hellcats Recovery Flasher

Hellcats Recovery Flasher contains 2 EBOOT.PBP the one is in ms0:\PSP\GAME\RECOVERY 

and the other one is in ms0:\PSP\GAME\UPDATE.

Copy the 5.00 ofw update to ms0:\PSP\GAME\RECOVERY 

FAQ: Can this brick my psp? 

ANS: Yes, if you turn your psp's power off upon the process of flashing the cfw to your psp's flash. Not doing so, 

will give you a very small posibility of bricking your psp.

5. Now run the HRF (Hellcats Recovery Flasher :) on GAME from your psp's xmb menu.

(what is xmb? - Xross Media Bar, your psp's menu interface, got it?)

Just go through the HRFs menu and just select which you think will change your psp to cfw that you want.

This will ask you some mind boggling questions that might change your mind and opt not to use this homebrew, 

We might had the same experience, I accidentally updated my fw to 5.03 ofw, Can't sleep for days hahaha. 

Although there's a possibility that it might brick my psp, this is my last resort before I bring my cursed psp to technicians (that would cost me).

Anyway, I had been through this and succesfully and got 5.00m33-6 cfw installed on my psp, 

Select 5.00 ofw (for 5.00 m33-6 cfw) when asked which ofw to use (or other lower fw ex. 3.71, 3.52 etc just have the ofw on ms0:\PSP\GAME\RECOVERY)

then choose to reset all the psp settings to default when asked. (I chose this one)

the process would take several minutes, just be patient, dont force shutdown.

When the process is complete, Your have to set your psp's settings just like a new one.

Check the fw and voila, this should be an M33 cfw. (5.00 m33-6)

 

If you have questions or difficulties getting through this instructions, feel free to leave comments. It would be greatly appeciated. :)

Soon I'll post the links for complete download of those files, I just have some problems uploading them right now.