How to Completely Erase an iMac Hard Drive

Written by elle smith
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How to Completely Erase an iMac Hard Drive
Protect yourself by wiping your iMac's hard drive cleanly and securely. (hard drive internals image by BigDog from

The iMac is one of Apple's most popular desktop computers, and as such, can fetch a good resale price if it's in good condition. It can also be a nice gift or donation. Erasing your iMac's hard drive prior to it leaving your possession is essential so that your identity can't be stolen or your documents recovered. Mac OS X makes it very easy to wipe the hard drive clean.

Skill level:

Things you need

  • Original OS X install disc
  • Optical drive

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  1. 1

    Back up all data you wish to keep to an external drive, DVDs or CDs.

  2. 2

    Insert your original Mac OSX install disk in the optical drive. Double-click on the window for "Install Mac OS X". You can only erase your hard drive while booting off the CD.

  3. 3

    Locate the "Disk Utility" application from the "Utilities" menu. Double-click to open the program.

  4. 4

    Note the two panes in the "Disk Utility" window. Look to the left pane and locate your computer in the list of disks, volumes or images. Select the hard disk you wish to erase, then click on the "Erase" tab in the right pane.

  5. 5

    Specify the format for the drive and choose a name by typing it in the "Name" box. a format and pick a name for the newly-erased drive. View custom erase options which provide extra security by clicking on the "Security Options" button in the bottom of the window.

  6. 6

    Carefully read the "Secure Erase" options window that opens. Select the security level you wish. Select one of the options ranging from "Don't Erase Data" which erases the information but can be likely recovered with most file recovery programs, to "35-Pass Erase", which provides the best security by writing over the data 35 times. Click "OK" when you have chosen your security option.

  7. 7

    Click "Erase" to confirm your decision to completely erase your iMac hard drive. Quit "Disk Utility" when complete.

  8. 8

    Reinstall the Mac OS X system software, or provide the disk with the computer when it changes ownership.

Tips and warnings

  • Back up your data prior to erasing your iMac's hard drive.

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