Internal HD only shows 139

[Tha General]

I have this rig:
http://www.emachines.com/products/products.html?prod=ET1161-05

I haven't found any bios update to it, but i always wonder why i have 139GB, but i have a Hitachi (160 GB). Same as my external hd, 500GB but only shows 465GB.
Not that 139 and 465 aren't enough, because its perfect haha, i was just curious.

 

[Matthew DeCarlo]

http://www.popularmechanics.com/how_to_central/technology/4206535.html?nav=RSS20

Your hard drive is advertised as having a 60GB capacity, but your computer shows only 55.8GB. 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.