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HP and Compaq Desktop PCs - Size of Disk Drive Does Not Match Specifications (Windows XP)

This document applies to HP and Compaq Desktop computers with Windows XP.

HP and Compaq computers with Windows XP preinstalled might appear to have a hard drive smaller than what is stated in the product specifications, documentation, or on the box. Windows reports smaller capacity in the Windows Explorer tool and in My Computer because it shows information about only one partition on the hard drive at a time.

HP and Compaq computers with Windows XP have hard drives that contain two partitions. The first is a hidden partition that contains system recovery information. The second partition is the usable space seen in My Computer or Windows Explorer.

Why is there a hidden recovery partition?

The information stored on the hidden partition is important system information and contains a backup of Windows XP and the original software. The partition is hidden to prevent accidentally deleting the files.

For HP and Compaq computers manufactured before Windows XP, recovery information was provided on CDs. HP no longer includes recovery discs for the following reasons:

  • Cost of CD production and testing

  • CDs are easily scratched and destroyed

  • CDs fail after prolonged exposure to sunlight

  • CDs can be lost or misplaced

  • Recovering from the hard drive is faster than recovering from CDs, and does not require disc swapping

You can create recovery discs or order them from HP. For more information, read Obtaining a Recovery CD or DVD set .


Viewing total disk space

Use System Information to view the total space and all the partitions on the hard drive.

  1. Click Start, and then click Run.

  2. Type the following in the Open box: msinfo32

  3. Click OK.

  4. Under System Summary, click the plus sign (+) next to Components.

  5. Under Components, click the plus sign (+) next to Storage.

  6. Under Storage, click Disks.

  7. The total disk space, and the two partitions on the hard drive are shown in the right pane.

Figure 1: Hard disk drive space

1 - Total hard disk drive space - 40 GB
2 - Hidden recovery partition - 4.41 GB
3 - Visible user partition - 32.85 GB


What is the difference between decimal and binary?

Different software and hardware vendors use different ways of measuring a gigabyte. How Windows displays the size of a hard drive mighty be less than the actual size reported by other sources.

Definition of decimal hard drive size

Manufacturers describe and advertise hard drives in terms of decimal (or base 10) capacity. In decimal notation, one megabyte (MB) is equal to one million bytes, and one gigabyte (GB) is equal to one billion bytes. The decimal system is what we use in everyday life.

Definition of binary hard drive size

Windows and other programs, such as FDISK (a Windows utility), use the binary (or 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 the hard drive capacity with FDISK, multiply the FDISK value (which is in base 2 notation) by 1,048,576 to determine the decimal equivalent.

An example using a 20.5 GB drive: FDISK displays the capacity of this hard drive as 19,603 MB (or 19.6 GB). This value represents the base 2 or binary capacity of the disk drive. To determine the equivalent base 10 or decimal capacity, multiply 19,603 by 1,048,576. This results in a value of 20,555,235,328 bytes or about 20.5 GB in decimal terms.


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