Safely delete a HDD We tell you everything so you know how to format a hard drive. Keep reading.

Why Safely Erase a Hard Drive

When your PC is changing hands, it is important to erase old data. It is useful for an individual, it is essential for banks and certain companies.

Therefore, it is necessary to ensure that the hard drives are completely erased to prevent the recovery of confidential data.

Step by step

Unfortunately, formatting the disks (even a low-level format) is not enough.

Indeed, if the format zeroes the disk, it is not zeroed "completely"

Take a disk to which we write the bits: 0101

Now format (write zero for everything)

But you can see there are some 1's, the zeros have slight residual magnetization. This magnetization can be solved with specialized devices, opening the hard disk (there are companies specialized in this type of recovery).

You can then deduce that you had 0101 data despite the format.

And it's even worse!

Previous data can be recovered, even when write on top. For example, in our record above, if you type 0011:

The two 1's do not have the same magnetization entirely: one is stronger than the other. Then you can figure out what you had before. The same for the two zeros.

Result: Pre-magnetization (0101) can be deduced despite the fact that zeros (0000) were written after other data (0011)!

In certain cases, it is possible to recover old data from a disk, despite formatting and destruction caused by new data. (This can only be done with specialized devices.)

It is important to find methods to erase hard drive .

For information, the U.S. Army does melt your hard drives to guarantee that nobody can recover the data entered in it.

Others use demagnetization devices that generate a powerful magnetic field (while destroying the hard drive).

We do not have all these means, but there is software that does what is necessary.

How to safely erase a hard drive

There are different methods and standards for deleting (DoD, etc.). However, considering the wide variety of methods for encoding information on magnetic media, the only solution that guarantees the best privacy is to perform numerous writing passes. This may seem small, but generating random data with a PC is not easy (the PC is deterministic by nature).

With an incorrect random number generator, it is possible to guess the following numbers by examining the past strings. It means that using a generator that is not good at random numbers (PRNG) allows you to retrieve your data despite everything.

One of the best random number generators is Mersenne-Twister, with a warranty period of 2 ^ 19937-1.

Software Darik's nuclear weapon and boot allows you to use Mersenne-Twister to erase discs. It is a mini Linux distribution that fits on a floppy disk (or CD). Just start the PC and start the 'erase'

Darik's Boot and Nuke supports XT, IDE, PATA, SATA, and SCSI drives.


For the file EXE (for floppy / USB), run it, insert the floppy or pen drive, select the reader and click the "Install" button. Therefore, the registration will be done on the floppy disk or pen drive.

The file ISO must be recorded with your recording software usual (take BurnCDCC or BurnAtOnce if you don't have one yet).


Start your PC with the floppy disk, the flash drive or the CD. On the screen, just click ENTER. Wait for startup to finish. Wait a moment, you will be greeted with the following screen:

(Note that once this screen is attached, you can remove the floppy / pen drive / CD, which is handy for doing multiple machines later)

Press M (the ? if we have QWERTY), and choose the "PRNG Stream" method (with the high / low arrows and Enter).

Press the value 8 (= number of passes) and click ENTER.

Then select the hard drive by pressing the key ESPA9O:

Then press the F10 key to start the deletion and wait for the treatment to finish.

ATTENTION: This will erase the entire disk (files, partitions ... everything!) Data recovery is impossible!

Note that after the last pass with the random data, the disk is erased with zeros.

So far the short tutorial to format your hard drive.