High-speed storage, conveniently placed buttons and easy-to-use backup features make the WD Dual-option Combo Drive an ideal solution for much-needed additional storage and a perfect place to back up your valuable data, music, photos and movies. 7200 RPM rotational speed Includes Dantz Retrospect Express backup software Preformatted for Windows; simply plug it in and go (Simple format instructions included for Macintosh) Designed for near-silent operation with WD's whisper-quiet hard drive Fast, easy connection to PC or Macintosh computers Cool, heat-dissipating case Stands vertically or horizontally Stackable Requires USB 1.1/2.0 or FireWire port on a computer running Windows 98SE/Me/2000/XP or Mac OS v9.2.2 or later; Mac OS X v.10.1.3 or later Dimensions - 8.61 (L) x 6.08 (W) x 1.74 (H)