I've read on other sites that you have to use the recovery option and reset the firmware before trying to root.
To be honest though your best bet is the XDA forums, you can find them here: http

/forum.xda-developers.com/
Every phone is different so it's not like I can help you by telling you how I rooted my G2/Desire Z. XDA is going to be your best bet, they're all Android devs.