The other question that needs to be asked: will this external hard drive spend its life sitting next to a desktop computer? Or will it travel with you and your laptop? If the former, then it'll be cheap ($0.40-60/GB should be the target price) to get a good-sized 3.5" external hard drive. If the latter, you're looking at around $0.80-1/GB for a good deal on a 2.5" external hard drive.