WD  My Book Essential 640 GB USB 2.0 Desktop External Hard Drive Includes - External hard drive, USB cable, AC adapter and Quick Install Guide Smart and energy efficient - Turns itself on and off with your computer Save and organize your digital photo collection USB 2.0 Serial Bus Transfer Rate - 480 Mbits/s System Requirements - Available USB port, Windows 2000, XP, Vista, Mac OS X 10.4.8 or later