Comment 5 for bug 1390890

Seems like OpenGL support depends on the video driver http://answers.microsoft.com/en-us/windows/forum/windows_7-hardware/opengl-driver-missing/d3f01e2c-831a-4277-8818-075ff46bc879

So, if the video card supports it and has an appropriate driver, OpenGL is available in Windows 7.

OpenGL has in principle been available in Windows XP, which is now oooold and past its end of life https://www.opengl.org/discussion_boards/showthread.php/161387-OpenGL-Windows-Vista

And here's the OpenGL documentation for Windows, just in case this might come in useful http://msdn.microsoft.com/en-us/library/dd374278%28v=vs.85%29.aspx

Aaand... a similar discussion on the 0AD forum: http://www.wildfiregames.com/forum/index.php?showtopic=16734&hl=opengl