I encountered this VSTI error when I tried to install the Powershell templates:

Installation stopped because the directory for the ProjectType value did not exist.  The project type is invalid for your installation of Visual Studio.

I don't see anything unusual in the .vscontent file either; just...

            <Attribute name="ProjectType" value="Visual C#"/>

Visual Studio is installed on D:. I have recently installed the 180 day trial edition of the Team Foundation suite; but, beyond that, there is nothing distinctive about the installation.