It has to do with numbering systems. By tradition and because computers work with powers of 2 Microsoft has used the definition that 1KB = 2x2x2x2x2x2x2x2x2x2 = 1024 bytes. Also, 1GB = 1024 x 1024 x 1024 = 1,073,741,824 bytes
Hard drive manufactures for marketing reasons define 1GB = 1000 x...