A hard drive read/write head at the Defense Computer Forensic Laboratory Sept. 9, 2010, in Linthicum, Md. Read/write heads ride on a microscopic layer of air that develops on the surface of the platter(s), some that spin up to 10,000 rotations per minute inside a hard drive. The slightest touch of a head onto a platter disk will cause physical damage and render that side of the disk unreadable. (U.S. Air Force photo/Lance Cheung)