That's actually not true at all. You get the difference in size because of what a gigabyte really is (1024MB) and what they call it at retail (1 million bytes). 1 byte is 8 bits, a KB is 1024bytes, an MB is 1024KB, etc. So when they sell you a hard drive with 1 million bytes, they call that 1GB, when in reality 1GB is 1048586 bytes. They call 1 billion bytes "1TB" when 1TB is really 1024GB, or 1073741824 bytes. So it looks like you're losing 70GB out of a 1TB HDD, when in actuality you're just being lied to by the manufacturer about how much capacity the drive has.