I have a question for T4220 owners who know how to mod their machines. Are you able to change out or add in a ATI or nVidia graphics card? I am planning on using this machine for art purposes; but I would really love a machine with one of those two graphics cards on them. But I was concerned one whether or not this is even possible. Please help. Also, which card would be better? I've heard that nVidia is better. Is that true?