HTC HD2 is originally running Windows Mobile 6.5 (WM6.5). However this video from pocketnowvideo shows that it is running Windows Phone 7. In last post we covered the HTC HD2 hack that will allow you to install Android. It seems like HTC HD 2 can run Windows mobile 6.5 and Windows Phone 7 and Android.
HTC HD2 hack to run Windows Phone 7 is from CotullaCode and this is on experimental level. It will be amazing if it can do multi boot HTC HD2 and switch in between the three operating systems.
HTC HD 2 Specifications