Hard drive size dropped after format

It is just HDD manufacturers using decimal byte 640,000,000,000 /1024^3= 596GB in correct binary bytes!

if the drive is a 640 gig drive your you partion the drive and format it you do lose space from the total hard drive. most vendor dont list the usable drive size just what the max size of the drive would be it you placed one bit on it. if your drive in windows was 640g and it now down to 595g then the program you used must of written the bad sectors onto the drive firmware there a defects list on all hard drives. then vendor makes these list and it stored on the controler. as a drive gets older bad spots do show up. some drive and controlers can mask out the spots and puts them in what called a glist or grown list. if the glist hit a set size then smarts if turned on starts warning users to replace the drive soon. the factory name for the defects is called a plist
http://www.dataclinic.co.uk/hard-drive-defects-table.ht...
you may want to look at the software you ran to see if it change those lists. if it did not then the hard drive did it itself.

Look at capacity as listed here in this article http://en.wikipedia.org/wiki/Hard_disk_drive

http://img840.imageshack.us/img840/5134/640v.jpg

That is correct size. The image posted is my 640GB hard drive. The total after formatting and partitioning is 596GB.

Best answer selected by laptop4079.