You need to download in and install HTC Sync, then uninstall it once it has finished. Go into control panel and then "add/remove programs". There will be two entries for HTC Sync. One is the program and the other is a driver package. Keep the driver package but uninstall the program. That sounds like your missing link. You should be able to root fine afterward.
I am one of the few, it seems, that is running stock group. I upgraded and now want to root. I have a Mac and need to know the best way to accomplish this. Is there an easier way to fully root without having to downgrade to 2.1? I am very green to all this rooting/custom ROM stuff and can't find a way to root with a Mac so I can wireless tether (this is 90% the reason I want to root in the first place).