500GB USB 2.5" External Portable Pocket Hard Drive SATA

Q & A:

My hard drive is advertised as having a 500GB capacity, but my computer shows only 465.76GB. What gives?

The discrepancy is the result of having two methods of measuring memory. Computers are binary, or "base two," mathematical systems, and in a binary world a kilobyte is 1024 bytes (2 to the 10th power). When computers were new, the geekerati referred to this as a "kilo." Noncomputer folks, however, understood kilo to mean thousand, and thought that 1000 bytes should equal a kilobyte. So, two different measurements of hard drive space were born. In 1998, the International Electrotechnical Commission (IEC) weighed in, defining 1 "gigabyte" as 1 billion bytes. Hard disk manufacturers agree, marketing their products using the rounder decimal value instead of the binary system. So, your drive is labeled as decimal ("giga") and your PC reads binary (IEC's term, "gibi"). Either way, you're getting the same bunch of bytes.

Ref: Hard-Drive Capacity Math: Tech Clinic By Carolyn Wilsey (Published in the January 2007 issue)

 http://www.popularmechanics.com/how_to_central/technology/4206535.html