Rename a .csproj or .vbproj to .msbuildproj and add to a new solution. Or do a search and replace in your existing solution: {FAE04EC0-301F-11d3-BF4B-00C04F79EFBC} with {13B669BE-BB05-4DDF-9536-439F39A36129}.
You can tell you’re using CPS because the “Refresh” button in Solution Explorer is removed.