Erase a Computer Hard Drive

Knowing how to erase data on your hard drive is an important skill to have, whether you are planning to recycle, sell or give away your old computer or just wipe the drive clean. Wiping your hard drive will keep your private information and financial details safe.

Steps

High Security Mac and PC Method

  1. Backup your system before doing anything. You should always backup important files before wiping (or erasing) your hard drive. Erasing your hard drive will make recovering your files challenging and you do not want to lose anything important.
  2. Use DBAN. If your computer contained any sensitive documents, photos or information which could be used to steal your identity, you will want to use a more secure method of removing your data. DBAN (or Darik’s Boot and Nuke) is a commonly used, free program used to securely erase your hard drive. It also works for Macs running at least OS X.
  3. Make sure your computer is set to boot from a CD. If it is not, follow these instructions.
  4. Type “dodshort”. When the computer boots from the disk, the easiest method to wipe the computer will be to type in either “dodshort” for a simple wipe or “dod” for something stronger (leave off the quotation marks for both). Both are the standard erasing methods for the Department of Defense and are very secure. You can use the interactive mode if you want more wiping options.
  5. Hit enter. Once you’ve entered your preferred method, hit enter. You’re done: it will start wiping. You will, however, need to reinstall an operating system and restore your files. [1][2]
    • It will take a VERY long time. Don’t worry. It’s normal.

Low Security PC Method

  1. Backup your system before doing anything. You should always backup important files before wiping (or erasing) your hard drive. Erasing your hard drive will make recovering your files challenging and you do not want to lose anything important.
  2. Reformat the hard drive using the installation disk.
    • Insert the disk into the CD-ROM tray. Reboot your computer. Watch carefully for a message to flash on the bottom of screen. This message will tell you what key you need to press in order to enter the Setup mode.
    • Press the key indicated during the boot process and enter Setup. Common keys are F2, F8 or F11. Look for an option to boot from a disk or CD and choose it.
  3. Select the "Reformat hard drive" option when prompted.
    • If you have more than one partition on your hard drive, the second one likely holds recovery information. If this is the case, you can leave that partition alone.
    • If your second partition holds an alternate operating system, you may want to delete it.
  4. Follow all prompts pertaining to the "reformat hard drive" process.
    • Choose the NTFS option for the drive's type.
    • Choose either Quick or Normal, depending upon your reasons for reformatting.
    • If the computer will be going to a new owner, choose the Thorough or Normal option for higher security.

Low Security Mac Method

  1. Backup your system before doing anything. You should always backup important files before wiping (or erasing) your hard drive. Erasing your hard drive will make recovering your files challenging and you do not want to lose anything important.
  2. Enable the Root User option in Utilities, accessed through the Finder.
    • Follow the prompts, entering your password as needed.
  3. Log out as the current user and log back in as the root user.
    • Click the Apple icon to switch users.
    • The root user login ID is "root." Enter the password you chose for this user during the root user creation.
  4. Insert the Mac OS X installation disk into the CD-ROM drive.
  5. Reboot the computer. Hold down the C key during the start-up function.
    • Follow the prompts and select the appropriate options.
  6. Select the default "Macintosh HD" volume, then click the Options button in the bottom left corner.
    • Choose the Erase and Install option for a clean reinstallation to erase data and reinstall the operating system. This is the most efficient method of erasing the contents of your Mac hard drive.



Tips

  • If you will be reinstalling Windows on your PC, understand that it will likely take a couple of days to completely reinstall the operating system, all necessary drivers and supporting hardware, additional programs and Microsoft Windows Updates. Continue using the Windows Update utility to search for, download and install updates until no more are available.
  • You will probably need to reboot your computer following each batch of Windows Updates that are downloaded and installed.

Warnings

  • The low security steps will not prevent trained computer professionals from being able to access any of your information, although it will make it considerably more difficult. The only way to completely prevent data access from a hard drive is to destroy the drive, though the described high-security method should be enough.

Things You'll Need

  • Computer
  • Installation disks
  • Active@Killdisk, DBAN, or similar software

Related Articles

Sources and Citations

  1. ↑ http://lifehacker.com/5835369/how-do-i-securely-wipe-a-computer-before-donating-it-to-charity
  2. ↑ http://www.dban.org/
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