After much praise from the fine IRC’ers in #psp-hacks, Team Reign has released what they call the “Complete AIO Upgrading & Downgrading Package.” Complete AIO (All-in-one) is a collection of packages to assist noobs with downgrading any PSP — from firmware 1.51 through to 3.03.
All 5 installers are packaged using ADePSP’s PSP Installer.
If you’re running any FW below 2.80 (1.51, 2.71, etc…), you’ll want to upgrade first using “280EasyUp” and then downgrade back to 1.50 using “280EasyDown.” You could also go straight to 3.03 — see below.
If you’re running a firmware version between 2.80 and 3.03 (2.81, 3.01, etc…) you’ll want to use “303EasyUp” and back to 1.50 with “303EasyDown.” — You get the idea. And yes, the unpatched Grand Theft Auto: Liberty City Stories UMD is still required.
After you’re staring in awe at your new 1.50 PSP… Why not upgrade it to Dark_AleX’s 3.10 OE-A
Although the installers include everything and copy everything to the correct location on your memory stick, I still recommend reading through the included text files for guidance and any potential gotchas.
As with any downgrader: USE AT YOUR OWN RISK!