UPDATE: Do not apply these updates if you are running non-stock HTC software ROM’s, even those that are based on stock HTC ROMs. Rather get an updated ROM from the group/person that made your ROM that include these updates. There is a real posibility that you might brick your phone if you apply these to non-stock ROM’s.
I have just noticed that there is a HTC Desire System Update rolling out in South Africa. Even though I run a rooted upgraded ROM (version 2.2), based on the official HTC ROM, I was also given the OTA download. So I am not sure whether this System update will take you from 2.1 to 2.2.
The version number is given as 2.29.405.2 and it is a 28.87MB update so I suggest you do it over a WIFI connection if you do not want to incur any mobile data costs. My build number before the update was 2.10.405.2.
You can check for the update from the Home Screen pressing MENU button then Settings / About Phone / System software updates / Check now.
I can only check on the MTN Network so am not sure whether it is available on any of the other mobile networks.

