I think we’re all familiar with the hard drive marketer’s definition of GB (gigabyte). Even though the computer world is built on powers of 2, and the closest to 1000 is 1024, the hard drive manufacturers decided they could advertise bigger drives if they use 1,000 as 1KB; 1,000,000 as 1MB; and 1,000,000,000 as 1GB.
When the size is small, there’s not much difference. When you are talking 100 GB, the 100,000,000,000 byte drive is technically only 93.13 GB.
One more piece of background: over the years, IDE-based hard drives have faced motherboards that could not recognize all their space. The first break-point was ad 8.4 GB. The next maximum was at 32 GB. Then, the original Windows XP would only recognize up to 132 GB. These were usually solved by software drivers from the motherboard or hard drive manufacturers. The Windows XP limitation was lifted by Service Pack 1.
You can further combine that with the calculations that Windows itself makes. Sometimes, Windows refers to the 1,000-based KB, MB and GB. Other times, it uses the 1,024-based KB, MB and GB.
Welcome to the confusion. The Windows XP “Help and Support Center” (which you get via most Microsoft Help menus) defines gigabyte as “gigabyte (GB)
1,024 megabytes, though often interpreted as approximately one billion bytes. Interestingly, they don’t bother to define megabytes or kilobytes. Usually the Help and Support Center is much more helpful than this.
and