This is a tutorial to show you how to downgrade you PSP Firmware 2.71. It has finally been done. Warning: Use of this downgrader could brick your PSP. While it is unlikely when used correctly, all modifications to the PSP's internal flash carry a small risk. Please use with care, PSPHome takes no responsibility for any damage you cause to your PSP.
Equipment!
>PSP
>PSP Power Pack
>PSP USB Cable
>PC with one USB Slot useable
>Sony Memory Stick Duo
Step 1
Charge up your PSP fully to ensure that the battery does not run out half way between downgrading your PSP!
Step 2
Download the update to 2.71 if your PSP is under that:
PSP Downloads | 2.71 Firmware Update (US)
Download the Easy 2.71 to 1.50 downgrader:
PSP Downloads | Easy 2.71 Downgrader Step 3
Insert a memory stick into the PSP, and then connect the PSP to the computer. Also remove any UMD's.
Step 4
If you have a 2.70 or under firmware PSP then create a folder on your memory stick called "PSP". Inside that create another folder called "GAME". Then inside the "GAME" folder, create another folder called "UPDATE". Inside this folder copy the file called "EBOOT.PBP" which can be found in the "2.71 Firmware" from the link you downloaded above.
Step 5
Turn on your PSP, and then go to the Game Menu of your PSP , select the last icon called "Memory Stick ". You should then see the screen below, Select the file called "PSP Update ver 2.71" and press the X Key.
Follow all the on screen prompts and the update should successfully happen in around 3 minutes.
Step 6
Once the update has been applied, go to "System Settings" under the home menu and select "System Information". If this says that the firmware is 2.71 then this was successful.
Step 7
Delete the folder called update from your memory stick
Step 8
Open the (.exe) of Xtrusions 2.71 to 1.50 downgrader. State the drive of your PSP and let it copy over the needed files to your memory stick.
Step 9
Now you are ready to downgrade. Make sure the AC Adapter is plugged in and go to the photo section of your PSP. As soon as you click X to enter the Photo Menu the downgrader will start automatically hopefully. If not scroll down to a file called "hw.tif" and click X. You will know if the downgrader has started because the whole of the PSP screen will go red and the memory stick light will flash. This process may take a few tries, if your PSP freezes and switches it self off WITHOUT the memory card flashing and, the screen not going red, turn your PSP back on and scroll over to the photo section again.
Step 10
When your memory stick light stops flashing, wait at least 30 seconds before full switching off your PSP. (To fully switch off you must hold the power button up for 10 seconds)
Step 11
Once your PSP has fully switched off, wait for 30 seconds and then turn on your PSP again.
Step 12
If all went well, the PSP will pop up a scary looking blue or red screen with multiple languages showing.
Blue Screen 
Red Screen 
Step 13
Read what it says and hit O to reboot. (If you get the red screen hold your power button up for 10 seconds until your PSP switches off. Then turn on your PSP again)
Step 14
Double check you have firmware version by checking your system information. (Settings> System settings> System information). If it says 1.5, you have successfully downgraded! You can now upgrade to custom firmware 3.03 OE-B!
Guide has been written for PSPhome. 
Leave me alone!!! 
Linear Mode
