I have found the following link for rooting several Android devices:
It seems quite easy to root, but how difficult is it to go back to unrooted once you've rooted?
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I'm using a HTC Hero and when I had to unroot my phone, I found the RUU for my phone. This in simple terms is a restore to your phone which the service provider uses to restore the phone to absolute stock. I'd check and see if you couldn't find the RUU to your specific phone!