How to Read the Boot Sector of a Hard Drive

Written by casey labine
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How to Read the Boot Sector of a Hard Drive
The boot sector tells a computer how to use the drive. (Hard Drive image by Tabitha Little from Fotolia.com)

Hard drives are composed of cylinders, disks and sectors. The first sector of each drive, located in the first disk of the first cylinder, contains instructions for how a computer should handle that particular drive when booting. This so-called “boot” sector facilitates housing multiple drives within a single system as well as splitting a single drive into multiple partitions. To protect users, however, a boot sector is not directly accessible through the operating system. It requires a special program instead. Windows Vista and later versions of Windows include a utility called BCDedit (Boot Configuration Data Editor) for just this purpose.

Skill level:
Moderate

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Things you need

  • Windows Vista or later

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Instructions

  1. 1

    Enter “cmd” into the search bar at the bottom of the Windows Start menu. This will open a command-line window with administrator privileges. BCDedit is a command-line utility and takes several optional parameters, so you can’t run it through Windows Explorer.

  2. 2

    Enter “bcdedit /v” at the prompt. By default, this will display the boot sector configuration for all connected drives.

    If the prompt instead returns an error message stating that it doesn't recognise the command, find BCDedit in your version of Windows (filename “bcdedit.exe”) using the Windows Explorer search function. Then manually navigate to this location in the command prompt by entering "cd" followed by the location of the directory (for example, "cd windows\system32"). From this location, entering “bcdedit /v” will always work correctly.

  3. 3

    Perform whatever operations you like on the boot sector using the additional BCDedit parameters (for a full list of parameters, enter “bcdedit /?” or see Resources). The “/v” parameter above instructs the application to display the full boot sector configuration rather than an abbreviated version. Other useful parameters include “/export,” which outputs the configuration to a new file, and “/import,” which can repair a corrupted configuration by restoring a previously exported backup.

Tips and warnings

  • BCDedit will most likely be stored in the System32 subdirectory of your Windows installation (for example: “C:\Windows\System32\”).
  • Depending on your reason for reading the boot sector and your operating system, a number of alternatives to BCDedit are available. In Windows Vista and Windows 7, for example, Bootrec in concert with Windows Recovery Environment will allow you to repair a broken boot sector.
  • Always take care in making changes to a boot sector. Errors may render the drive unusable until they are repaired.

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