SlashGear

Now why on earth would you want to downgrade your PSP’s firmware and lose all the wonderful features that the new software brings? Well, for hacking and homebrewed games, of course! Hackers have devised and released a special PSP 2.5/2.6 downgrader, which will knock the PSP’s firmware back to v1.5. Version 1.5 is far easier to hack than the newer firmwares have been, with several homebrewed applications supporting only this firmware. However, should you enter into this rather dangerous of exploits, be warned: doing this incorrectly runs the risk of ruining your expensive handheld investment…permanently. So let the user beware; but if homebrew is your thing, it might be worth the effort. If you went ahead and installed PSP Firmware 2.7, however, you’ll have to wait for an updated downgrader to be released.
[via Kotaku]