From time to time, we have a newer version of Visual Studio and have problem open older project because of the non-support by the new Visual Studio. We can force open it by changing the <ProjectTypeGuids>.
e.g. I wanted to run the project NerdDinner. I couldn't open it directly by Visual Studio 2013. The program refused the upgrade the "Web" project "NerdDinner" ("NerdDinner.Tests" was ok). So, I edited the NerdDinner.csproj. From this page, I know the MVC project type guid of different version of MVC. So, I changed from version 2 (F85E285D-A4E0-4152-9332-AB1D724D3325) to version 3 (E53F8FEA-EAE0-44A6-8774-FFD645390401). It then compiled and run fine.
Now, we can upgrade the nuget packages and bring up the references so that it works well with the newer version of Visual Studio and .Net framework. That's another story though.
