Easily Convert Your Windows Apps Into Windows 8 Metro Apps
Another thing worth mentioning is that you only need to change 1 line of code to turn your metro apps running on Windows 8 into an app that runs on Windows Phone 7. Handy? It is.
Also, converting your existing applications into metro apps for Windows 8 requires little code changes. In fact, the changes are so minimal you can do it in a few minutes. How awesome is that?