IBM full-size Thinkpads could be configured with a second battery or a second 2.5" hard drive in the spot we think of as where the optical drive goes -- user-in

IBM full-size Thinkpads could be configured with a second battery or a second 2.5" hard drive in the spot we think of as where the optical drive goes -- user-interchangeable, even. There have been superportables all along without built-in optical drives, such as the ThinkPad 560 (1996).