OpenGL is not a standalone software you can download; rather, it is a set of specifications implemented through your graphics card (GPU) drivers. To get on a Windows 7 64-bit system, you must install the latest official drivers for your specific graphics hardware. How to "Download" and Update OpenGL 3.1
Before providing the download steps, it is crucial to understand that OpenGL is not a typical software library that you download and install manually. Opengl 3.1 Download Windows 7 64 Bit