I highly recommend the ta-082 downgrader instead, even if you don't have ta-082.

First upgrade to 2.71.
http://dl.qj.net/Firmware-2.71-PSP/p...8046/catid/163

Then check if your mobo is ta-082
http://www.maxconsole.net/content_img/ta82spot.jpg

Then downgrade.
http://downgrader.lan.st/ta082down.rar

If you don't have a ta-082, just skip the idstoragechange part.

2.71 downgrader?!!!
Sorry, I didn't read the whole post!