Thank you Very Very Much for your Tutorial. i downgraded the PS3 from 4.21 to 3.55. and did the De-Hashing
i am glad you have made a successfull downgrade.
it looks like a slap in the face for me in regards to the psp service tool lol.
i will have to add it to the guide (i still dont know why it never worked on any of my psp's.)