Hard Drives, commonly referred to as a computer hard drives, hard disk drives or disk drives, are non-volatile storage devices which store digital data on rapidly rotating platters (discs) with magnetic surfaces. Early computer hard disk drives had removable media; however, all hard disk drives today are sealed units with internal fixed media. Hard disk drives are available in a number of interfaces, including USB External Hard Drives, Firewire External Hard Drives, SATA Hard Drives & IDE Drives.