Open GL is what COH is programmed in. New and fancy games like HL2 and Doom are programmed in Direct3D. OpenGL is a very old language (think voodoo 2) and COH was written in it for compatability. So unless your onboard card takes from the main memory COH *should* run which looking at what you wrote, the card has it's own memory.
Now next step, what does COH do when you try to run it? (it goes without saying that you update drivers and what not, but you already knew that, right?)