Which guide are you using?

Fwiw, I recommend this one purely because the previous procedure worked for me, and it's been regularly updated by the very people who found the original root exploit.

 

What is the current firmware build number installed? It's listed in Settings/About phone/Software information (iirc) and should be 1.34.x. If it's 1.72.x or 1.82.x then you'll need to downgrade as described in steps 1-12 of the guide. Once you've got 1.34.x installed follow the other guide I linked to in order to get perm-root.

 

hi..
im using this link as reference while doing rooting on my desire z..

HTC Vision - XDA-Developers

(under topic "How To Get R/W Access (Permanent Root / "Permaroot") using gfree v0.5 ")

they ask me to downgrade the phone 1st before i can cont rooting the phone. so i went to this link for downgrade process as they told.

[GUIDE] Downgrade your Desire-Z from 1.72 to 1.34 (and get root and S-OFF) - xda-developers

when reach step 11, my phone cannot proceed the hboot process..it say "main version is older!
update fail!"..

my current info ~

android ver : 2.2.1
software no : 1.82.707.1

anyone here can help me to fix this problem?

 

Did you check which INFOCID applies to your handset, as explained at the top of the downgrading guide? Unless yours is one of those listed you'll need to make a goldcard in order to override the CID lock and flash the older firmware.