Now you need to download the Original 2.1 rom that is straight from HTC. Get it Here:
http://shipped-roms....6984_signed.exe
Ok, Now your phone must be connected in the Charge only mode and with usb debugging enabled.
Now open the rom that you downloaded. Just to clarify this is the official stock rom.
Just tick all the boxes and keep clicking next. It will then show you the version on your phone (it should be 1.19.xxx.xx blah blah) the it should have an update button. click that update button then click next.
Your phone should start to update. It should take about 5-10 minuted and it should complete everything by its self. It may seem like it freezes a couple of times and even when the update program is finshed and closed your phone will still be busy for a couple of minutes.
Eventually it should finish and you should be 100% debranded. Now search for updates and you will get 2.2