The game should run fine on the Lower/Medium setting on your laptop with its native resolution. If you look at the performance of the 8600, its about the same as the 7900GT(desktop version) if I recall correctly. The 7900GT can run Supreme Commander at Medium specs(1440x900 resolution). Supcom uses the same engine as Demigod.
Edit: if its an M8600 GS forget about running the game. If its an M8600 GT then it should run on the minimum setting, I compaired the mobile version of the 8600 a bit too much with the desktop version of the 8600.