Root HTC Desire 2.2 with Unrevoked.

Ref:

http://www.thedroiddemos.com/2010/09/20/how-to-root-the-desire-with-unrevoked-3-21-video-walkthrough/

http://gfans.bryan.tw/2010/09/22/801

Note: 1. need to connect the USB in HTC SYNC mode.

2. seems to be easier to have it work with windows then mac.