What you see isn’t a Windows Phone 7 hack on an iPhone. Instead it is just a Windows Phone 7 theme that makes your iPhone look like as if it is running the OS. Called OS7, the theme is currently available in beta and can be downloaded from here. You can install one by following the steps below:

1. Install Backboard from Cydia.
2. Make sure you have created a “Default” backup, if not, press the add button in Backboard and give it a name.
3. Go on your device and click on this link: backboard://http://wyndrepo.googleco…es/OS7Beta.zip
4. Press “Yes” and wait for it to download. This may take a few minutes depending on your internet connection.
5. Select OS7 from Backboard. Press Install. Respring.