A group of Russian hackers have done something that Microsoft said wouldn't happen - shoehorned a working Windows Phone 7 Series OS ROM onto an HTC HD2 handset.
All the important stuff such as WiFi, GPS and Bluetooth seem to work, although it's claimed that the graphics driver is dodgy and the handset can sometimes be a little laggy.
Remember though that this "upgrade" from Windows Mobile to Windows Phone 7 OS breaks some stuff ... like copy'n'paste and multitasking!
The team claim that they'll release a "beta" version soon, which I'm assuming is an euphemism for a dodgy release. Use at your peril folks!