Although Microsoft did not make Mango available as an update to all WP7 devices, it had a released to manufacturers (RTM) version of Mango. This rom was leaked on the Internet and a lot of the old Windows Phone 7 had the capability to update their rom to the latest Mango albeit unofficially. Surprisingly, one phone that wasn’t even meant to be a WP7 phone which is the HTC HD2 had the same update as well thanks to a poster from the xda-developer forum.
Those that still have their warranties on may want to avoid porting their HD2 to Windows Phone 7 since it would null their warranty. However, those that insist can definitely give Windows Phone 7 a shot with their HD2 devices.
The process of changing to the Mango version can be complicated and lengthy as well. In fact, some users said that it took at least 3 hours to get it done and if anything goes wrong in the process, it had to be redone. Nonetheless, those that are experienced can still get it to work with ease. To know more about the process, click here.