I was getting the below message from Visual Studio 2010.
\"This project is incompatible with the current version of Visual Studio\"
In my case it was an incompatible Project Type. Editing project file and removing ProjectTypeGuids node resolved the issue of loading the project (I had already re-targeted the framework version as advised here).
Probably the project type is not supported in the (most likely) NEW version of VS, so you will have to adjust (update) the code to work properly (if possible), but at least you can see the content through VS.