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Size of Hard Drive Does not Match Specifications (Windows XP)

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This document pertains to HP Notebook PCs with Windows XP.
HP and Compaq Presario computers may appear to have a hard disk drive that is smaller than the size that is stated in the product specifications, documentation, or on the box. Windows reports smaller hard disk capacity in the Windows Explorer tool and in My Computer because it only shows information about one partition on the hard disk drive at a time.
HP and Compaq Presario computers may have hard disk drives that contain two partitions. The first partition is hidden and contains the system recovery information. The second partition is the usable space that can be seen inside My Computer or Windows Explorer.

How to view total disk space

To use System Information to view the total space and all of the partitions on the hard disk drive, follow the steps below.
  1. Click Start , and then Run .
  2. Type msinfo32 in the Open field, and then click OK .
  3. Click the plus sign (+) that is next to Components to expand the list of components (see the figure below for an example), click the plus sign (+) next to Storage to expand the list of storage devices, and then click Disks .
    Figure 1: System summary
    Image of the system summary screen.
    The total disk space, and the two partitions on the hard disk drive, are shown in the right-hand pane. The example shown in the figure below displays 37.27 GB (gigabytes) as the total hard disk drive size, as reported by Windows. This equals a little over 40 billion bytes in exact size when converted to decimal notation (see the What is the difference between decimal and binary section below). The size of the hard disk drive that is shown in the figure below is a true 40 GB hard disk drive.
    Figure 2: Hard disk drive space
    Image of the hard disk drive information with disk size and partition size highlighted.
    1 - Total hard disk drive space
    2 - Hidden recovery partition
    3 - Visible partition (space shown in My Computer)

What is the difference between decimal and binary?

Different computer systems use different ways of measuring a gigabyte. The size that Windows displays as the size of the hard disk drive may be less than the actual size.

Definition of decimal hard disk drive size

Hard disk drives are described and advertised by manufacturers in terms of decimal (base 10) capacity. In decimal notation, one megabyte (MB) is equal to 1,000,000 bytes, and one Gigabyte (GB) is equal to 1,000,000,000 bytes. The decimal system is the system that we use in everyday life.

Definition of binary hard disk drive size

Windows and other programs, such as FDISK, use the binary (base 2) numbering system. In the binary numbering system, one megabyte is equal to 1,048,576 bytes, and one gigabyte is equal to 1,073,741,824 bytes.

Convert binary size to decimal size

When determining hard disk drive capacity with FDISK, multiply the value shown in Windows or FDISK (displayed in base 2 megabytes) by 1,048,576 to determine the decimal equivalent for the capacity of the hard disk drive.

An example using a 20.5GB drive:

FDISK displays the capacity of the hard disk drive as 19,603 MB. This value represents the base 2 or binary capacity of the hard disk drive.
To determine the equivalent base 10 or decimal capacity, multiply 19,603 by 1,048,576. The result of this multiplication is a value of 20,555,235 bytes, or approximately 20.5 GB in decimal terms.