Erm. It's actually a theme that came preinstalled (as well as over 100 more) with the custom Windows 7 OS I have. The theme itself is called "Windows Phone 7". The OS is Windows 7 Infinium. It's just a custom built OS from the Enterprise Edition of Windows 7. Comes preloaded with a ton of stuff. :S
Here's another screenshot for your liking. xD -- http://i.imgur.com/2OEyK.png