http://blogs.technet.com/b/uspartner_ts2team/archive/2010/03/29/free-windows-phone-developer-kit.aspxWindows Phone 7 Series holds a promise to be an amazing personal mobile phone with new innovative user interface and functionality , as well as a great development platform on which you can quickly and easily build games and applications. With a myriaden-USTelligent Evolution Platform Developer Build (Build: 5.6.50428.7875)