When an SSD, hard drive, or old laptop is sold, people usually delete their personal files beforehand. However, many users do not realize that the hard drive often still contains information of great interest to the curious or criminals, for example:

• Browser history can allow conclusions to be drawn about browsing behavior and bank details.
• Stored email traffic reveals details of business transactions and provides information about subscribed streaming services and times when no one is home.
• FTP tools such as Filezilla offer to save access data so that the user does not have to enter them again and again, thus opening access to the FTP servers of companies and organizations.
• Browsers open the way to accounts and services of all kinds via their password managers.

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Full Hard Drive Wipe Required

Windows and applications hide your personal data in many places in the file system and in databases such as the registry, where it is almost impossible to find. It is therefore advisable to completely erase the disk before putting it back. How to do this depends on the type of storage media.

In the private sector, virtually all computers today contain an SSD. The drives are several times faster than hard drives and they are robust. With SSDs, it is very difficult, and often impossible, to recover deleted files.

This is easier with mechanical hard drives, but they are almost only found in NAS devices and enterprise storage systems, where high capacities and lower acquisition costs are more important than speed.

USB sticks and external hard drives, on the other hand, obey completely different rules than internal models. Let’s start with the internal SSDs.

Deleting data partitions on an SSD drive

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The first step is to delete the data partition(s), if present, i.e. drive D:, E:, F: and others.

This can be easily done by formatting with Disk Management: right-click on the Start icon in the taskbar, go to “Disk Management”. Alternatively, you can also use

diskmgmt 

in the search box on the taskbar. Right-click on the partition you want to delete and go to “Format”.

In the next dialog window, remove the check mark in front of “Perform a quick format”: this will actually delete the files from the drive and not just their entries in the Master File Table (MFT). Then start the process by clicking “OK”.

Removing the system partition with a CD or boot key

Deleting the system partition, i.e. the C: drive, is a bit more complicated. Since Windows is installed on this drive and cannot delete itself, you need bootable installation media from which to perform the removal process.

If you have a Windows DVD, use it to boot your computer. If you don’t have a DVD, you will need a bootable USB drive for the process.

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The easiest way to create such a stick is to use the Media Creation Toolavailable for free from Microsoft. After accepting the license terms, click “Next” and indicate under “Select the media to use” that you want to create a USB key.

A key with a capacity of at least 8 GB is required. Insert the key and click “Update Drives” if necessary. After clicking “Next”, the Media Creation Tool deletes the existing files on the drive and fills it with Windows installation files.

The finished stick is bootable. Start your computer with it and click “Next > Install Now” when the country settings appear. Click “I don’t have a product key” and select one of the Windows versions offered.

Check the box next to the license agreement, click “Next” and select “Custom: Install Windows only.” Then select the system drive – you can recognize it by the name you gave to the partition – and click “Delete”.

You can then cancel the installation by closing the window. The SSD is now completely empty, the C: drive no longer exists and is listed as unallocated storage.

With an SSD, it is also almost impossible to restore previously saved data. This is mainly due to the Trim function (see next section).

Secure deletion using the Trim command

The Trim command ensures that SSDs are written evenly, extending the life of the drive. The command is now supported by virtually all SSDs for the SATA interface.

It has been included in Windows since version 7 and is active by default. Normally you don’t need to do anything else, the Trim function runs automatically in the background. If you delete data from an SSD, Trim notifies the drive that those storage areas are no longer in use.

The next time the computer goes into sleep mode, the drive’s Active Garbage Collection ensures that any areas marked by Trim as no longer valid are freed for deletion.

Permanently delete data from hard drives

The situation is somewhat different with hard drives. They do not have a Trim command, so data can still be recovered after deletion and even after formatting with some effort. But here too there are ways to make data permanently unreadable.

For data partitions you can use tools like Ascomp secure eraser. This will not only delete the files contained in the drive but also overwrite them with random data.

With Secure Eraser, click “Securely erase hard drive/partition” on the startup screen, select the drive in the next window and click the down-pointing arrow next to the “Start the process” button. ‘erasure’.

This opens a drop-down menu where several methods of overwriting with data are available. A single overwrite is enough to render files unreadable, so select the “Low” or “Normal” setting. Then click “Start Removal” to start the removal process.

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You have to do it differently with a system partition. Since Windows cannot delete itself, you need a live system with which you can boot your computer from a CD/DVD or USB stick.

You can then delete the data on C: from there. Unlike an SSD, it is necessary to then overwrite the deleted memory areas with new data so that the original contents can no longer be reconstructed.

Free software Darik’s Boot and Nuclear Weaponabbreviated DBAN, has proven itself in this area. Download the ISO file first. Then connect a USB stick to your PC. It doesn’t have to be big; the tool only requires around 16MB of space.

Download and install it Rufus freeware and enter the DBAN ISO file in the “Startup Type” field. Then let Rufus create a bootable USB drive and boot your PC from this drive.

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Darik’s Boot and Nuke is based on a simplified Linux system without a graphical user interface. After startup, you can use the command

autonuke 

to automatically delete and overwrite all data on your hard drive. You can also select the options you want by pressing the Enter key.

Securely Erase USB Drives

Although USB drives and hard drives are closely related to SSDs, they do not support the Trim command. So you also need to format the stored files after deleting them.

The aforementioned Ascomp Secure Eraser software can only erase and overwrite hard drives and SSDs. Free software Erasing the disk suitable for USB sticks.

Open the program, select the drive and click “Wipe Disk”. In the first window, the wizard will ask you for the desired file system. Normally, NTFS is the best choice. After clicking “Next”, select how the data should be overwritten. Here, “One Pass Zeros” or “One Pass Random” are enough.

In both settings, Disk Wipe performs data overwriting process. Click “Next”, type erase everything In the input field, click “Finish” and confirm the deletion process. The program will then first format the disk and then start overwriting individual memory cells.