After a few (de-)installation cycles I finally figured out the OpenGL header story for the WinDoze versions of GHC: * GHC 5.04 contains a GL subdir with OpenGL headers below include\mingw. Those headers seem to come from a Cygwin distribution, despite of the misleading pathname. * Alas, GHC 5.04.1 and GHC 5.04.2 are not shipped with OpenGL headers. * The WinDoze installer packages for *both* GHC 5.04 and GHC 5.04.1 are called 'ghc-5-04-1.msi'?! This is where part of my confusion came from. I suggest changing this on haskell.org/ghc. * As an aside, the GHC 5.04.2 installer comes with superfluous compilers and support libraries for C++, Objective-C and Fortran77. Leaving these out would reduce the unpacked size of GHC by 6.3MB. :-) Some more confusing facts about MinGW and Cygwin: * MinGW's headers GL/gl{,u,ext}.h are identical to the ones from Cygwin's w32api/GL. The GL/glext.h header is lying about the OpenGL version on WinDoze, pretending it's 1.3. * MinGW comes with a GLUT libraries, but not with a corresponding GL/glut.h header. What to do in all this chaos? As the simplest short-term solution I've packaged the following headers into a ZIP file: include/mingw/GL/gl.h (from Cygwin's w32api/GL == MinGW's GL) include/mingw/GL/glu.h (from Cygwin's w32api/GL == MinGW's GL) include/mingw/GL/glut.h (from Cygwin's GL) include/mingw/GL/glext.h (from Cygwin's w32api/GL == MinGW's GL) It is available at: http://haskell.org/HOpenGL/releases/OpenGL-includes.zip Simply unzip it into the installation directory of GHC 5.04.1 or 5.04.2 (e.g. C:\ghc\ghc-5.04.2 for the default 5.04.2 installation). It would be nice if upcoming WinDoze installers for GHC were shipped with those headers. Cheers, S.