PHP Code:
http://www.topsony.com/forum/showthread.php?t=45
I have a Z550 too, and i'm really proud too say i managed to do all that
I used the information in the above post, and it worked great for me...
Technicly, there's almost ni way of screwing up your phone if you use this tutorial... but be carefull and read it with attention...i think you will need to install far again..try the one linked in the post, cause it worked perfectly for me
and don't worry, any mistake you make can be repaired by starting over... Good luck!!!