Before you sell, give away, or throw out a computer, you need to wipe its hard drive clean. That’s true even if you encrypt your hard drive (which you should) and the same goes for external hard drives and USB drives.
Why? Because your hard drive is a malicious hacker’s dream. It is filled with the kind of information that makes identity theft and social engineering a cakewalk. You might as well be handing your clients’ bank accounts over to the bad guys.
Whether your old computer is bound for a new owner or a landfill, make sure you wipe the hard drive before it leaves your control. Simply deleting your user account is not sufficient to protect the information. You actually need to wipe the drive.
The easiest way to do this is with Darik’s Boot and Nuke, or DBAN. DBAN is free, open-source software that uses military-spec methods to eliminate all traces of data on your hard drive. Essentially what it does is overwrite the data on your hard drive with random characters again and again until there is nothing left to recover.
Before you wipe your hard drive, make sure you have what you need to reinstall the operating system if you want someone to be able to use your old computer. Most manufacturers include either a system restore disc or leave a system restore partition on the hard drive that you can use to restore the computer to its factory-fresh state. If you aren’t sure how to do this, check the manufacturer’s website for directions before you boot up DBAN.
Using DBAN is simple. Download it from
dban.org, then burn it to a CD, DVD, or USB flash drive. Boot your computer from that CD or DVD (usually you have to press a function key during boot to give you the option to boot from the CD instead of booting up Windows as usual) and follow the instructions. If you used an external hard drive to transfer your files, plug it in before you boot DBAN and wipe that drive, too. Just don’t nuke the system restore partition if that is how you intend to restore your computer to its factory-fresh state.
Once your hard drive is clean, you can either dispose of your computer or restore factory setup, update everything, and hand it off to its next owner.
Revised and republished 2016-04-29.