Yeah USB HDD rules, its really lifesaviorsometimes that can fit even your pocket. Plus with your tablet laptop its ultimate decision for digital artist . But this drawing is awesome . And you drawed it with only PS cs3 and zbrush jn your laptop. Just amazing and feels impossible for me.
Perhaps you should invest in one of those HDD SATA USB cradles. The newer versions are even USB 3.0. They are great, I can't do without. Think an external HDD, except for the fact you can swap out the hard drives like say, a Nintendo cartridge, and since it's USB you can move any file between any computer.