C++ – Cannot open include file: ‘ntddk.h’: No such file or directory

In practice, the difference is in the location where the preprocessor searches for the included file.

For #include <filename> the preprocessor searches in an implementation dependent manner, normally in search directories pre-designated by the compiler/IDE. This method is normally used to include standard library header files.

For #include "filename" the preprocessor searches first in the same directory as the file containing the directive, and then follows the search path used for the #include <filename> form. This method is normally used to include programmer-defined header files.

A more complete description is available in the GCC documentation on search paths.

This header is a part of the MFC Library. VS Express edition doesn't contain MFC. If your project doesn't use MFC you can safely replace afxres.h with windows.h in your terrain2.rc.