The project type is not supported by this installation

Question

Open up the .csproj file for your solution in wordpad or some text editor. Look for the ProjectTypeGuids. They indicate the required supported types for your solutions. Search the internet these GUIDs to find out what they require. For example E53F8FEA-EAE0-44A6-8774-FFD645390401 means it requires "MVC 3.0"

edit please see the answer further down, which is about 18 months newer, and actually solves the problem. This historically once-accurate answer is no longer as accurate. Leaving intact after the break for this reason. - thanks - jcolebrand

---

What edition of VS do you use? VS2008 Express, Standard, Pro or Team System? VS2010 Professional, Premium or Ultimate? I would expect that the project you downloaded was created using a higher edition of Visual Studio and uses some of those advanced features. Thus you can not open it.

EDIT: It is also possible that you lack some advanced frameworks like newer versions of Windows Mobile SDK, but if I recall correctly,the error message in such case is different.

For Visual Studio 2010 (prolly also for other versions):

If you are opening an ASP.NET MVC project make sure that the correct MVC version is installed on your PC. If you try to open an ASP.NET MVC 3 project, first close all your visual studio instances and install MVC3: http://www.microsoft.com/en-us/download/details.aspx?id=1491

For other ASP.NET MVC versions download them from www.asp.net/mvc or via Web Platform Installer 4.0.

Instead of searching fr the GUIDs, you can simply delete the GUIds tags. Then try opening the project again. The second time opening you should get a more reasonable error message.

For instance my issue was that I did not install SharePoint Developer Tools when I installed Visual Studio 2010 on my development Virtual Machine. So when I tried opennign the project after deleting the GUIDs, VS2010 told me the path it was looking for did not exist.

Therefore VS2010 was looking for a SharePoint library that was not installed. I simply had to run the install again, and then add that feature.