Smartphones have progressed by leaps and bounds, yet they are far behind the humble PC in some respects. Modular phones have attempted to bring upgradability, but few phones seriously considered giving you freedom of choice when it comes to the operating system. The HTC HD2 is legendary in that respect. It launched in 2009 with Windows Mobile 6.5, heavily modded by HTC. Since then it has run Windows Phone 7, Windows Phone 8, Android, Microsoft's Android, Windows RT, Firefox OS, webOS, MeeGo, Tizen... iOS is probably the only mobile platform that eluded the fabled HD2. There are some...
Source: http://www.gsmarena.com/counterclockwise_htc_hd2_and_friends_run_any_os_under_the_sun-news-24179.php
