Securely Erase Your Hard Drive Before Sale or Recycling

A couple of months ago, I took several old desktop computers to a computer recycling center. All of them were at least five years old and severely underpowered for my needs. Before I packed the computers in my car, I removed all the hard drives. Most of these computers hadn’t been powered on in several years, so I had no idea what might still be stored on the drives. If you ever decide to get rid of your old computer, I strongly recommend taking a similar precaution before risking giving away personal data.

Preparing Your Computer for Sale or Recycling

There are procedures you can take to reduce the risk of data leakage when you sell or donate an old computer. Restoring the operating system to factory settings is probably good enough to keep out the average user. But what if the person receiving your computer isn’t average?

Doing the long version of a disk format before re-installing the operating system will stop more people, but in most cases any $50 hard drive recovery program will find some of your old data. I know I’ve recovered data from a drive after a format. What you really want to do before getting rid of a hard drive is securely erase the drive to be sure nothing is left behind.

This is why I didn’t send the hard drives to the recycling center. A small part of me was uncertain about contents on the drives that I might still want. A much bigger part of me was paranoid about giving away sensitive data like old bank information and whatever other digital exhaust I might have accidentally left behind. A secure erase of the hard drives would leave me more confident about sending them away, but the day I undertook the cleanup project, I hadn’t wanted to figure out if each computer would boot, use a secure hard drive erasing utility, and then pack them in my car for recycling.

At the time, it was faster to simply open the computer case, disconnect the computer power cable and drive cable, and remove the hard drive completely. I ended up with a much smaller pile of stuff, in the form of several hard drives.

How To Securely Erase A Hard Drive

The steps I use to make sure my data is unrecoverable are fairly straight forward. You need the included disk formatting function of Windows and a free utility from Microsoft TechNet call SDelete. The key thing that SDelete does that you can’t do with a simple format is overwrite all the free space on the drive. When you format a drive, Windows marks the space on the drive as available, but it doesn’t necessarily truly overwrite all the data previously stored in that space. SDelete actually writes useless data over any data that previously existed, making it far more difficult to recover any files from the drive.

This video below walks through the process step by step.

Start by Formatting the Drive

Start by using the Windows drive format function to format the entire drive as one large drive partition. You can easily do this from Windows Explorer by right clicking on the drive you want to format and choosing Format from the right-click menu. Uncheck the Quick Format option so that Windows performs a more thorough format of the drive. Like I said earlier, the full format will make it harder for most people to recover data, but in my own testing I have been able to recover some data following this step.

Use SDelete to Clean Free Space

After the format of the drive, the entire drive is one large block of free space. SDelete will write data over this space in order to make it nearly impossible to recover any previous data. SDelete meets a U.S. Department of Defense standard for data destruction, so you can feel fairly confident that it’s doing the job it should.

To get started you need to download SDelete and unzip it using Windows built-in Extract feature, the application will be available from the folder location where you unzipped it. You will need to navigate to that folder from the command line. You can access this by using the Windows Key + R to pull up the Run dialog and typing cmd followed by the Enter key.

After you have the command line open, type cd C:Users{username}{path to sdelete}SDelete, replacing username with your username and the path with the folder location. The easiest way to do this might be to copy the path from Windows Explorer and paste it in to the command line by using the right-click paste function.

Once you are in the SDelete directory, simply type sdelete.exe -c {driveletter}:
For the drive I used as an example in the video this looked like sdelete.exe -c e:

Caution: Be sure that you perform this operation on the drive you want to clean, otherwise you could lose data.

SDelete takes some time to process, so don’t expect it to complete instantly. For large drives, it could take a couple of hours. Once it’s complete, your drive should be unrecoverable for virtually all tools.