http://msdn.microsoft.com/visualc/quake/

"Download and Build Quake II for .NET
Vertigo Software Inc. has released Quake II .NET, a version of id Software's popular Quake II game ported to the Microsoft .NET common language runtime (CLR) using Microsoft Visual C++ .NET 2003.

Download Quake II .NET from Vertigo Software, Inc., including full source code and project files for Visual C++ .NET 2003, as well as a white paper describing the effort."

I think this is a part of Microsoft's effort to raise the profile of C++ in .NET.