Library Technology - Reviews, Tips, Giveaways, Freeware

Library Technology – Reviews, Tips, Giveaways, Freeware

Securely Erase Data from Internal or External Hard Drives on Windows or Mac

Posted In Windows, OS X - By Jack on Wednesday, September 28th, 2011 With No Comments »

Whether you are selling a hard drive and need to delete your data from the drive or simply need a completely clean and formatted hard drive to work with, securely erasing the drive is simple, using some freeware utilities or even some default utilities built-in to Windows or Mac.

Erasing a hard drive to the point where no data is recoverable is recommended whenever you sell a hard drive. This process involves not only reformatting the hard drive, but also writing over the existing data with new data. There are multiple ways to wipe a hard drive, internal or external, for both Windows and Mac. Let’s start with how to erase a hard drive for Mac.


OS X has a built-in utility called Disk Utility that is capable of securely wiping and erasing hard drives. However, the process will vary, depending on whether you are erasing an internal or external hard drive:

For internal hard drives

When selling a Mac computer, you will want to secure erase the data from theinternal hard drive prior to sale. This process is very simple. To get started, insert the first install disc that came with your Mac when you purchased it. It should be labeled something like, MacBook Install Disc: 1.

The disc may auto launch, but just ignore any on-screen prompts. Restart your computer using the path Apple Logo > Restart. Immediately upon reboot, once you hear the audible startup chime and see the Apple Logo, hold down the c key. Continue to hold the key down until you see the spinning wheel below the Apple logo.

By holding down the c key, we are booting from the install disc, rather than the hard drive. Once the OS X install screen appears, click Continue to proceed to the next screen. At this point, hover your mouse over the very top of the screen. This should trigger the Mac OS X navigation bar to appear on screen. Select Utilities >Disk Utility. Once Disk Utility opens, select your Mac’s internal hard drive from the devices list, located along the left side of the Disk Utility window. Click theErase tab.

Set the Format: to Mac OS Extended Journaled and enter a Name: for the hard drive. For Apple default, the hard drive should be named Macintosh HD. Next, click the Security Options… button. From here, you can select an erase level. The 35-pass takes a long time, but it is the most secure, as it writes over the hard drive 35 times. For a quick and secure erase, choose the zero or 7-pass options. Finally, click the Erase… button to proceed to erase the data on the drive.

That’s all there is to it. Once the disk finishes erasing and writing you can reinstall OS X, or simply leave the disk the way it is, securely deleted and formatted to Mac OS X Extended (Journaled).

For external hard drives

The process of securely erasing an external hard drive is the same process as above. However, it can be done directly within OS X, so you don’t have to reboot and boot from an install disc. Simply navigate to Finder > Applications > Utilities > Disk Utility to access Disk Utility.


Windows has more specialty apps and freeware programs to choose from, for deleting hard drives securely. For example, the program Active Kill Disk is a completely free program that makes it simple to delete data from drives. Another good program is DBAN, which is also completely free. In Windows, it is better to secure wipe hard drives using an app, as Windows 7 does not incorporate a user friendly way to zero disks. Although, if you simply want to format a disk, you can do so using Disk Management, Start > Search Programs and Files > DiskManagement.

For this demo we will be using Active Kill Disk. So to get started, download Active Kill Disk and install it onto your PC (link above).

Launch Active Kill Disk using the path Start > All Programs > Active KillDisk > KillDisk for Windows.

Kill Disk has a minimal interface and is very simple to use. Simply select the hard drive (internal or external) that you want to erase, from the disks menu located on the left side of the screen.

Once a drive is selected, the Kill button will become active. Click the Kill button. This will bring up the Kill menu, which lets you select custom preferences for the hard drive erase. Click to check any options that you want and click the Start button. Note that you can also choose an Erase Method:

That’s all there is to it. Now, you just have to wait for the disk to format and be written over. After that is done, you will have successfully, and securely, wiped the hard drive.

Any other recommended options for erasing Mac or PC hard drives? Leave a comment! Have a solid state drive? Check out our review of SSDs here.

About -