How old is your computer? OpenGL 2.0 has been around since 2004 so most computers should have it. What graphics card do you have? Updating the graphics card driver (from the manufacturer's website) might fix the problem depending on how old your graphics card is.
The kongregate version has a fallback html5 canvas renderer (which is really ugly - and it will warn you about if it uses it) that allows the game to run even if you don't have OpenGL 2.0+ - but the full version can't use it (it's not HTML5).