Windows repords HDD size incorrectly

Archived from groups: microsoft.public.windowsxp.customize (More info?)

I Have just installed a Maxtor SATA 200 GB hard drive in my computer.
Partition Magic reads this drive at slightly over 200 GB, but Windows
XP reports it as 193GB. What gives?

Archived from groups: microsoft.public.windowsxp.customize (More info?)

PM wrote:
> I Have just installed a Maxtor SATA 200 GB hard drive in my computer.
> Partition Magic reads this drive at slightly over 200 GB, but Windows
> XP reports it as 193GB. What gives?

Just for future reference:

Advertised --- Actual Capacity
10GB --- 9.31 GB
20GB --- 18.63 GB
30GB --- 27.94 GB
40GB --- 37.25 GB
60GB --- 55.88 GB
80GB --- 74.51 GB
100GB --- 93.13 GB
120GB --- 111.76 GB
160GB --- 149.01 GB
180GB --- 167.64 GB
200GB --- 186.26 GB
250GB --- 232.83 GB

The actual formatted and usable storage area is often less than what is
advertised on the boxes of today's hard disks. It's not that the
manufactures are outright lying, instead they are taking advantage of the
fact that there's no standard set for how to describe a drives storage
capacity.

This results from a definitional difference among the terms kilobyte (K),
megabyte (MB), and gigabyte (GB). In short, here we use the base-two
definition favored by most of the computer industry and used within Windows
itself, whereas hard drive vendors favor the base-10 definitions. With the
base-two definition, a kilobyte equals 1,024 (210) bytes; a megabyte totals
1,048,576 (220) bytes, or 1,024 kilobytes; and a gigabyte equals
1,073,741,824 (230) bytes, or 1,024 megabytes. With the base-10 definition
used by storage companies, a kilobyte equals 1,000 bytes, a megabyte equals
1,000,000 bytes, and a gigabyte equals 1,000,000,000 bytes.

Put another way, to a hard drive manufacturer, a drive that holds 6,400,000
bytes of data holds 6.4GB; to software that uses the base-two definition,
the same drive holds 6GB of data, or 6,104MB.

So, be prepared when you format that new 160GB drive and find only 149GB of
usable storage space. Isn't marketing wonderful?

--
Shenan Stanley
MS-MVP
--
How To Ask Questions The Smart Way
http://www.catb.org/~esr/faqs/smart-questions.html

Archived from groups: microsoft.public.windowsxp.customize (More info?)

On Tue, 16 Aug 2005 08:34:12 GMT, Andrew Bailey wrote:

> I always thought it was because Windows keeps a portion for hidden system
> (hive) files.
>
> Andy

There's a legacy 8MB that shows up when looking at the drive with something
like Partition Magic. Other than that, the difference in size is simply a
matter of math. The actual space on the drive is the same regardless of
which method is used to describe/calculate that space.

--
Sharon F
MS-MVP ~ Windows Shell/User