This is a Portable Harddrive which is powerd through USB....Not the 3.5' Harddrive which requires additional power adaptor. I am buying this one to upgrade my MAC.
The Western Digital 500GB Elements portable hard drive is simple, easy-to-use, light and easy to carry. There is no need to carry a bulky power adapter; this drive gets its power from the USB cable.
500GB Hard Drive Capacity
480 (Max) mbits/sec Transfer Rate