THIN PSP'S CAN'T HANDLE FIRMWARE 1.50!
Do not attempt to downgrade these below 2.5 I believe.

This tutorial now tells you how to install the LATEST Dark Alex Firmware, 3.80 M33.

For the most up to date custom firmware, check out Dark Alex's Website.

Thank you Dark_Alex.

***Note: This involves writing to Flash0. If you follow my steps this will work most of the time. There is always a danger when you mess with the Flash0, so use caution. Also, firmware 1.50 will not work on slim psp's. You should also have a decent size memory stick, at least half a gig.***

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Part 1. Downgrade to 1.50. (Fat PSP's ONLY.)

Step 1. If you have version 1.5 Firmware, skip to step 6. If you have a custom firmware, skip this section. Otherwise, Upgrade to 2.80. To do this, create a folder in (/psp/game/update/) and extract the 2.80 eboot.pbp to that folder. Execute the Update program from the PSP game menu.
2.80 upgrade eboot.pbp

Step 2. Grab a copy of the following:
Move everything inside of HEN D's MS_ROOT folder to the root folder of your psp, such as E:\ or J:\.
Move everything inisde of the Downgrader's MS_ROOT folder to the root of your psp, such as E:\, F:\.
Rename the 1.50 Eboot.pbp file to UPDATE.PBP, and put it in the (/psp/game/UPDATE) folder.

Step 3. Go to your PHOTO folder, and open HEND 2.80 folder. You should see a flash of blue. If you don't and it shuts off, try the following:
To check if the program works, try running the cube demo from your GAME, MEMORY STICK menu.

Step 4. Charge your psp to at least 75%, preferably 100%. Run the program "Update X.YZ" from your Game Folder. You need 75% power or more in your battery. When it finishes, it will ask you to press X. Press X.

****EDIT, ADDED****
If you have firmware 2.81-3.03 psp,
here is how to downgrade to 1.50.

Step 1. Make sure you have a copy of Grand Theft Auto: Liberty City Stories UMD. Then see if it has a 2.00 update on it, or a 2.60. If you have a 2.00 update on that umd, you can do this downgrade! Otherwise, stop here for now.

Step 2. Grab a copy of Noobz's 3.03 Downgrader here, a copy of 1.50 here, and a copy of 3.03 here.

Step 3. Upgrade to 3.03.

Step 4. Install the 3.03 Downgrader by unzipping it to the root of your memory stick (Like to E:\ or G:\, where your psp is).

Step 5. Grab your copy of the 1.50 EBOOT.PBP, rename it to UPDATE.PBP, and move it to (/psp/game/UPDATE).
It should now be (/psp/game/update/update.pbp).

Step 6. Start GTA. It should get to "loading savegame", then the screen will clear to black and fill with a light blue color, then the PSP will reset itself.

Step 7. Check that HEN is running by going to "Settings", "System Settings", and "System Information". It should now be "303 HEN". If not, go back to Step 6.

Step 8. Go to "Game", "Memory Stick", and run "Update x.yz". If your motherboard requires patching, it will be automatically patched, so don't worry about it. Press "X" to begin the downgrade.

(If it comes up saying that the settings are corrupt, press x to continue. Load the included NetConfigBackup application in your PSP, and select "restore", this will restore the backup of Network Config done automatically during the downgrade.)

If you have firmware from 3.03-3.50 psp,
here is how to downgrade to 1.50.

Step 1. Make sure you have a copy of Lumines I UMD.

Step 2. Grab a copy of Noobz's 3.50 Downgrader here or here, a copy of 1.50 here, and a copy of 3.50 here.

Step 3. Upgrade to 3.50. Once this is done, delete the folder (/psp/game/UPDATE).

Step 4. Install the 3.50 Downgrader by unzipping it to the root of your memory stick (Like to E:\ or G:\, where your psp is).

Step 5. Grab your copy of the 1.50 EBOOT.PBP, rename it to UPDATE.PBP, and move it to (/psp/game/UPDATE).
It should now be (/psp/game/update/update.pbp).

Step 6. Start Lumines, and press x to start the game. The screen will clear to black, and fill with a light blue color... then the psp will reset itself.

Step 7. Check that HEN is running by going to "Settings", "System Settings", and "System Information". It should now be "350 HEN". If not, go back to Step 6.

Step 8. Go to "Game", "Memory Stick", and run "Update x.yz". If your motherboard requires patching, it will ask to be automatically patched, so don't worry about it. Press "X" to begin the downgrade... DO NOT UNPLUG PSP, TURN OFF, OR TRY TO RESTART.

These next two steps are sorta optional:
Step 9a. If it says settings corrupt, press x to continue... you will have to redo the net connections for the psp, thats all.

Step 9b. You can load NetConfigBackup application, and select restore, which will restore the network settings that existed before downgrading.

Here is a video of this operation: Youtube, PSP 3.50 Downgrade Video

<you can always stop here if you want, and have 1.5>


Part 2. The Update steps.


NOTE:These next steps are a tad convoluted. It involves updating to several firmwares, since at the moment there is no single method of updating. Sorry for this.

Step 1. (For 1.50, Fat PSPs.) Go to the below link, and download the "Firmware 3.52 M33" Zip. Unzip the contents of "1.50only" (kxploitpatcher and kxploitpatcher%) to your game folder (/psp/game/). Activate this program from the PSP game menu.
Dark_AleX's Firmware 3.52 M33

Step 2. From the same zip file, copy the "M33CREATOR" to your game folder (/psp/game/) so that it is (/psp/game/M33CREATOR/).

Step 3. Get a copy of the eboots to update the psp to 1.5 and 3.52, and rename them to : 150.PBP and 352.PBP.
Place these two files inside the folder (/psp/game/M33CREATOR/). Run the program by going to your game menu and selecting "3.52 M33 CREATOR".
This doesn't write to flash, it just makes a file for the updating process.

Step 4. Make sure your psp is charged ABOVE 75% (100 is fine).

Step 5. Go again to Games/Memory Stick on your PSP, and execute "3.52 M33UPDATE". You'll have to press X to agree to the installation.
When finished, press X to shut down and reboot manually. Don't forget, you can't skip step number 6 if you want to get to the most recent firmware, ok?


<you can always stop here if you want, and have 3.52 M33>


Step 6. Ok, we now have a 3.52 M33, which we need to upgrade to version 3 of all things. Grab the 3.52 M33-3 update, and unzip it to the root of your PSP. Run the update program from the Game menu once more!

<you can always stop here if you want, and have 3.52 M33-3>


If you already had 3.52 M33-3 or higher, this is where you start.
Step 7. FINALLY! We can now upgrade to the most recent firmware, version 3.80 M33! Download version 3.80 M33, and copy the "UPDATE" folder into (/psp/game/) to create (/psp/game/UPDATE/).

Step 8. Grab a copy of Sony's firmware 3.80, rename it to 380.pbp, and move it to (/psp/game/UPDATE/).

Step 9. Run the update program from the game menu. At the end when you are asked to reboot the
PSP pressing X or O, do it (VERY IMPORTANT!).

Thats it! You now (finally) have the most recent firmware! Here's hoping that the next version will be a lot easier to work with.

Part 3. Converting a PSX game into a PSP Eboot.
To play a PSX game, you just convert it using the PC program "Popstation" included inside of the 3.03 OE-C Update... However, I have done something more.
I have modified the default program, and created one called "AutoPopstation4".
3.03 OE-C Update, By Dark_Alex
AutoPopstation4, By TheAceOfFire

How to use AutoPopstation4.
1. get AutoPopstation4, By TheAceOfFire

2a. Move any ISOs, BIN's, you made to the same folder as AutoPopstation3.bat.

2b. Run AutoPopstation4.bat.
This will tell you if you have made any errors, and will explain each step...

2c. Copy/Move the folder (It will have the same name as your ISO) inside of the "Result" folder to (/psp/game).

Again, to get my distribution AutoPopstation4, click here.

How To Uninstall a Custom firmware. (DO NOT USE ON SLIM PSPS!!!)
The one SURE FIRE WAY that I know of to uninstall involves the parts we have already gathered! Note, slim PSP's can not handle the 1.50 firmware.

1. Gather together the 1.50 eboot and Generic Downgrader for 2.71.
Generic Downgrader for 2.71
1.50 Eboot

2.Unzip the Generic Downgrader, and copy the contents inside MS_ROOT to the root of your memory stick.

3. Rename the 1.50 Firmware eboot from EBOOT.PBP to "UPDATE.PBP".

4. Move "UPDATE.PBP" into (/PSP/GAME/RECOVERY).

5. Run the program from the recovery menu. (Hold down "R" Shoulder button as it starts.)
Easy, no?

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Help me!:
1. Your links dont work, Jerk!
Oh, sorry, Just search Google for the programs you need:
~3.52 eboot psp
~3.80 eboot psp
~1.50 eboot psp
~"Homebrew Enabler for 2.80 revision D", also known as "Hen D", check noobz
~"Generic Downgrader for 2.71" By Dark_Alex, who made most of this.
~Firmware 3.52 M33.
~Firmware 3.52 M33-3, aka the third update.
~Firmware 3.80 M33.
~Also, check DarkAlex's web site, and Noobz.

2. How do I 'install' homebrew? Huh?
Easy. If the zip folder has a folder called "msroot" or "psp", just dig into it untill you find either one or two folders with the name of the homebrew you want.
If it is for 1.0, it will just be (name).
if it is for 1.5, it will be two folders, (name), and (name%).
Unzip these folders to your (/psp/game150) folder, and they will be available under the game option on your menu (check the memory stick option).

3. How do I add in a new Plugin?
To add your own, just move the prx to (/SEPLUGINS).
If it is used in the xmb, add the line ms0:\seplugins\NameOfYour.prx to vsh.txt.
If it is used in a game, add the line ms0:\seplugins\NameOfYour.prx to game.txt.
To enable the plugin, completely turn off your psp, hold down the right sholder button, and turn on your psp to enter the boot menu.
Choose the "Plugins" option, and press x on the list item with the NameOfYour.prx option so that it says (Enabled). Then either choose back, Exit, or restart the PSP.
^_^ Done!

4. What if I (someday) have a problem with Dark_Alex's Firmware?
When you turn it on, hold down the right shoulder button. This opens a menu that can either repair it, return it to version 1.5, hide corrupt icons, hide the psp bling thing, etc. Check it out sometime. It is sorta an "unbricker". Neat.

5. What if I wanna upgrade to a Sony Firmware?
Use the "Generic Downgrader for 2.71" to downgrade to 1.5 (or just use the menu from holding down the right shoulder button during boot), then upgrade as normal.

6. How do I get rid of corrupt icons?
One, use the right sholder button menu (hold down during boot.).
or Two, rename the folders
from (blah) to (__SCE__blah) and
from (blah%) to (%__SCE__blah).
or Three, see number 8.
Problem solved. Neat.

7. Where does the folder RECOVERY go?
(Asked by 'dq9', answered by TheAceOfFire)
To USE it, you will need to move that folder to (/psp/game/).
If you are just keeping a copy in case of an emergency, just leave it in the root of the memory stick, and move it when needed to (/psp/game/).

QuickJump Downloads for the PSP
PSP-Homebrew and Info Site

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If I left anything out, let me know. All of this is done WITHOUT me linking to either firmware dumps or illegal files, and all of the software belongs to their respective owners. Thanks go to them, all I did was enjoy their software. ^_^ Very fun.