i think all the portables and even the Mini as well have the graphics chip built into the logic board, along with the CPU and whatnot, so essentially it's not removable or upgradable (not sure about the iMac but wouldn't be surprised if that was the same). i believe the only components that are upgradable in apple laptops are bluetooth, wireless, hard drive, optical drive, and ram of course. but it can be quite a feat to replace some of those things (at least, it sounds like a pain to me). i would think most PC laptops have the graphics chip built into the logic/mother board as well, though i read that nVidia has a technology out called MXM that turns the graphics stuff into a module that it can be taken out and upgraded and stuff, though i'm not sure if it'll really catch on.