I assume you mean an upgrade after you actually have bought a 12" with a combo drive. Since it is possible to get a 12" with a superdrive, a superdrive could be installed later; however, this would be difficult. Since the superdrive in the powerbooks is specially designed to fit in a notebook, it is not something you can just go and buy anywhere. You would first have to find an apple authorized reseller who could order you the powerbook superdrive from apple, and then you would have to have it installed or install it yourself. So while it is possible, it is not very practical and if you foresee yourself needed a superdrive go ahead and buy a powerbook with a superdrive. If you have already bought one, see if you can return it or buy an external drive.