How to completely erase a Hard Disk

Have you ever sold or given away your old laptop or desktop to replace it with a new one? Certainly you might have at some point of time in life and you must also have backed up your data and then formatted your hard disk before selling or disposing it.

But did you know that data can still be retrieved from a formatted hard disk or storage media? Imagine if the data falls in the wrong hands of a Scammer and then that data can be used to learn about your browsing habits, your personal information, banking data and more. Scary isn’t it?

I know it is scary, but with the right kind of tools you can save yourself this fright. But before we take a peep in to some of my favourite tools, let’s understand a bit about how data is stored and what happens when you delete or format a disk.

Tossing files into the computers Recycle Bin and then emptying the trash deletes the record of the file, but not the actual data the file points to. Think of it as removing the labels from folders in a file cabinet. The folders and information in them still exist, even if retrieving the data takes more time and effort. When you delete a file from your computer, it’s not really gone until the areas of the disk it used are overwritten by new information. If you use the normal Windows delete function, the “deleted” file is sent to the Recycle Bin until the space it uses is required by other files. If you use Shift-Delete to bypass the Recycle Bin, the space occupied by the file is marked as available for other files. However, the file could be recovered days or even weeks later with third-party data recovery software. As long as the operating system does not reuse the space occupied by a file with another file, the “deleted” file can be recovered.

The same is true if you format a hard drive. It is still possible for someone with the right tools to retrieve data on the drive. Yikes!

The same goes with formatting a hard drive. The kind of formatting that we do normally is high level formatting. What high level formatting does is set up the file system from scratch and in the process the information where files were stored is removed. In short, high level formatting is the process of writing the file system structures on the disk that let the disk to be used for storing programs and data. Formatting a disk this way removes all information about the pointers in the File Allocation Table (FAT) which point to the location of a file on the disk. This means that old data still remains loaming in the dark.

Low level formatting on the other hand re-initializes the disk and resets the values of each and every one bit, to zero. Remember, data is stored in digital format as 1 & 0? Low level formatting is the process of outlining the positions of the tracks and sectors on the hard disk and writing the control structures that define where the tracks and sectors are. This is often called a “true” formatting operation because it really creates the physical format that defines where the data is stored on the disk.

Here are some tools that would help you to safely and securely wipe out the slate clean before you sell it or recycle it.

Darik’s Boot and Nuke: Darik’s Boot and Nuke (“DBAN”) is a self-contained boot disk that securely wipes the hard disks of most computers. DBAN will automatically and completely delete the contents of any hard disk that it can detect, which makes it an appropriate utility for bulk or emergency data destruction.

DBAN is a means of ensuring due diligence in computer recycling, a way of preventing identity theft if you want to sell a computer and a good way to totally clean a Microsoft Windows installation of viruses and spyware. DBAN prevents or thoroughly hinders all known techniques of hard disk forensic analysis.

DBAN is a free software product that can be used at home or in a business at zero cost.


SDelete: Good old Microsoft with their free command line utility called SDelete. SDelete is a command line utility that takes a number of options. SDelete (Secure Delete) implements the Department of Defense clearing and sanitizing standard DOD 5220.22-M, to give you confidence that once deleted with SDelete, your file data is gone forever.


Eraser: Eraser is a freeware and open source security tool to completely remove data from your hard drive. Eraser is an advanced security tool for Windows which allows you to completely remove sensitive data from your hard drive by overwriting it several times with carefully selected patterns.


Evidence Nuker: This piece of software allows you to choose which items would you like to erase such as Address Bar History, Browser Cache, Cookies, Documents History and much more. Evidence Nuker features several shredding methods, including 5220.22-M, the military standard set by the Department of Defense.


The next time you think of selling your laptop, desktop or dump your USB Pen drive, make sure that the data on the storage medium is properly erased and not just deleted.

Remember, protecting data sometimes means erasing it.

If you know of any more tools that you think will benefit the computing community, do share them as part of the comment. Many will surely benefit from it.

  1. Hi Sir,

    Please check your link it is getting redirected after getting first impression with message “page cannot find…”

    Sonu Chauhan

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