OK, I have posted two files :
Please login to see this link. >>> for Windows Phone SDK 7.1
Please login to see this link. >>> for Windows Phone SDK 8
I will turn it into an option in the Application properties, but for the moment Yves is absent so I cant do it.
Just copy one of the files in you data\runtime\XNA\Phone directory, and remove the 7 or 8 so that it replaces the existing one. This file is not to be opened, it contains the template Runtime project.