I am trying to change to use Visual Studio 2013 instead of Code Blocks for my IDE. I am trying to run a project I already made and when it tries to build, it gives me numerous random errors in the gl.h file which I didn't even write. I saw others had this same problem and one solution was to add #include <windows.h> so I did that, and it reduced the number of errors. I tried adding it to more places and it continued to reduce the number of errors. Why do I need that in Visual Studio but not in Code Blocks? Is there some way to put that information somewhere once to fix the problem everywhere?