OpenGL is not software. It is implemented by your graphics card and the drivers for your graphics card.
Either your card supports OpenGL 2.1 or it does not. If it doesnt there is nothing you can do except to upgrade your hardware.
However, it might also be that your drivers are outdated. Try downloading the latest drivers for your graphics card and perhaps they will support OpenGL 2.1 by now. If they dont there is nothing you can do.