Lumines and GTA downgrading is dead.

Mod any PSP regardless of firmware version

Pandora's Battery & The Magic Memory Stick
Unbrick / Downgrade & Install Custom or Official Firmware.

All the software and information you need is here:
https://www.noobz.eu/joomla/

PlayStation Portable Homebrew Wiki

TIPS:
Making your own PSP PSX Icons:
A helpful tip when making your own pops icons and backgrounds.
To disable the annoying PIC0.PNG (HotShots) image.
Create a new *blank* text file and then rename it "PIC0.PNG"
Rename "new.txt" to "pic0.png" to make your own.
Then include it with your other custom icons.
December 25th 2006 5:09pm

Extracting your own PSP firmware files
What you will need:
PSAR Dumper for 2.80 through 3.80
Most recent Sony Update: EBOOT.PBP (the "official updater" that you want to extract)
Archive of past firmware updates: PSP Vault
PC
Memory stick with at least 128MB of free space.

PSP Brew
Theses are old instructions.
PSP Brew is no longer needed to extract the DATA.PSAR
The Newest PSAR Dumper will decrypt the files right from the EBOOT.PBP

PSP Brew is still good for editing custom Icons and Backgrounds.
It is still needed to extract firmware versions lower than 2.80
1. Download PSP Brew
2. Install it on your PC
3. Use it to extract the DATA.PSAR from the EBOOT.PBP (The Eboot.PBP you downloaded from Sony)
4. Copy the DATA.PSAR to the root of your psp memory stick
5. Copy PSARDumper to the Game150 folder of your memory stick and then run it.
6. Wait while it will extracts files from the DATA.PSAR file to a folder called F0 onto the root of your memory stick.
7. Copy the F0 folder to your PC and Delete what you don't need off your memory stick.

*Notes:

Regarding failed flash attempts resulting in a bricked PSP.
General good practices and tips.
Little known problems.

Pandora's battery is only needed to put the PSP into service mode
At your own risk:
You only need the battery to put the PSP into service mode.
Once its in service mod you can plug-in the DC Power Supply and flash the PSP.

The PSP will stay in Service Mode even if its rebooted until the DC is disconnected.

So put Pandora battery in
Boot to Pandora menu
Plug in DC
Remove Battery
Flash away at full power.

Press the L button and Triangle to bypass the battery check
Use at your own risk!

Don’t try to write anything to the PSP’s flash memory, like themes, until you have upgraded to an OE or M33 firmware.
The native 1.5 firmware does not contain a recovery menu.

Solutions to solve strange problems after a flash are:
System Settings > Restore System Defaults
Or
Recovery Menu > Advanced > Format F1 and Restore System Defaults
This deletes the config.se file that is recommend as a solution to registry problems.
Toggling F1 and deleting it yourself works just as well
The PSP will recreate the file the next time it is restarted.

Lexar memory cards have problems loading plug-ins.

Flashing the firmware on your PSP is always dangerous and could likely render your PSP useless.

There are different versions of PSP motherboards and some down graders do not recognize this well or at all.
Incorrect, unsuccessful or un-patched TA-82+ motherboards result in a dead psp.

The Noobs 3.03 and 3.50 down graders do the best job of patching motherboards.

Counterfeit memory cards lead to data read and write problems.
If this happens during firmware re-writes this is not a good thing.
Test your memory card to see if it’s counterfeit.
Don’t a use counterfeit memory card to flash your PSP.

Power supply issues: Dead or dying battery and or a faulty power supply.
Always flash using a fully charged battery with the power supply plugged in.

Restarting before a flash is complete = dead psp.

Disconnecting a power supply during a flash write = unfortunate.

Use firmware auto-installers at your own risk.
Really means “Look I made this, I hope it works”