How To Make Sure Information On Your Old Computer Is Really, Truly Deleted
It Isnât As Simple As Pressing âDeleteâ And Emptying The Trash. Hereâs A Step-By-Step Guide.
â By Sean Captain | June 17, 2025 | The Wall Street Journal (WSJ)
Illustration: Jon Krause
Spring-cleaning season is almost done, and it is time to finally get rid of that old computer. But be very careful before you sell, give away or recycle it.
You could be handing over sensitive information.
Even if you think you deleted everything on it, your old computer may hold lots of personal items you donât want anyone seeing. In a 2019 study by the University of Hertfordshire (funded by security tech-reviews site Comparitech), researchers purchased 200 used hard drives from the U.S. and U.K. An analysis found data remaining on 59% of the drives, including passport and driverâs license scans, bank statements, utility bills and âintimate photos.â
Just pressing âdeleteâ and emptying the Trash in macOS or the Recycle Bin in Windows wonât do the trick. Thatâs because your computer maintains an index of where every file resides. Deleting a file erases only its entry in the index, telling your system that it can put new files in that space. But until the system actually does put new files there, the old ones remain accessible. Simple consumer-level file-recovery apps can get at itânever mind professional-grade forensic software.
Hereâs how to make sure your data is really goneâeven on a computer that wonât start up.
Back-up And Log Out
Start by backing up anything you want to keep. You could drag files onto an external hard drive or use backup software such as the Time Machine app in macsOS. You can also back up to the cloud using Microsoft OneDrive, Apple iCloud, Google Drive, Dropbox or other services. (Donât empty the Trash or Recycling bin. The wipe process will take care of this.)
Next, log out of applications or games with an online component, so the license is no longer associated with your old computer. Also do this for services like Gmail or Facebook, and web browsers like Chrome that sync your data onlineâon the admittedly remote chance that an incomplete wipe allows the next owner to access those accounts.
Another step for any type of computer is making sure your files are encryptedâscrambled in a mathematical operation based on very long strings of random numbers and letters called encryption keys. The wiping process will delete the keys to make sure any files that may remain on the machine are unreadable.
What you do next depends on your operating system.
Clearing Out A PC
Windows 10 and the current Windows 11 have a feature called âReset this PC,â which, with the right settings, thoroughly wipes your data. First, make sure your operating system is up-to-date, as Microsoft recently fixed a bug that sometimes caused the reset process to fail. Press the Windows key, search for âupdatesâ and select âCheck for updates.â Install any that are available.
Now check on encryption. In Windows 10 or 11 Home editions, press the Windows key and search for âdevice encryption settings.â Click âDevice encryption settingsâ on the next screen, then make sure the switch next to âDevice encryptionâ is toggled on. Windows Pro, Enterprise and Education editions have an encryption utility called BitLocker. To enable it, click the Start button, type âbitlockerâ and select âManage BitLockerâ from the list of results. (All versions of Windows 10 and 11 also encrypt deleted files.)
Now youâre ready to wipe. Tap the Windows key again, search for âReset this PC,â then click on it. On the next screen, tap âReset PCâ (Windows 11) or âGet startedâ (Windows 10), and on the following screen, click âRemove everything.â On the next screen, select âLocal reinstall.â (If this doesnât work, try the âCloud downloadâ option.) Then click âChange settings,â and on the following screen (under âClean data?â), toggle the switch to âYesâ and press âConfirm.â On the following screen, press âNextâ (Windows 11) or âResetâ (Windows 10). On Windows 11, you will press âResetâ on one more screen. Then let the process run for a few hours.
âReset this PCâ deletes your files, apps and settings, logs you out of your Microsoft account and disables the âFind My Deviceâ feature so the computer is no longer associated with you. Then the serious wiping starts. The encryption keys are deleted, making any encrypted data irretrievably scrambled, and the Clean data option overwrites the ones and zeros that had encoded data on your drive. A clean copy of Windows is also installed.
The MacOS Method
Appleâs âErase Assistantâ feature made its debut in 2021âs macOS 12 Monterey. If your current OS is older, you may be able to update it. To update an older OS to Monterey or a later one, click the Apple menu, then âSystem Preferencesâ and âSoftware Update.â If the update process doesnât work, jump to âIf all else failsâ below for another option.
As with Windows, the âErase All Content & Settingsâ process should start with encryption. On newer Macs (starting between 2018 and 2020, depending on the model), data is encrypted automatically. Just to be safe, though, turn on a feature called FileVault that adds encryption to older systems and an extra layer to newer ones. Click the Apple icon, then âSystem Settingsâ (or âSystem Preferencesâ in Monterey). In the next window, click âPrivacy & Securityâ (or âSecurity & Privacyâ), then click FileVault.
Now it is time to wipe. Click again on the Apple icon and âSystem Settingsâ (or âSystem Preferencesâ), click âGeneralâ on the left, then âTransfer or Resetâ on the bottom right. Finally, on the next screen, click âErase All Content & Settings.â (In Monterey, youâll go there directly from âSystem Preferences.â)
This process signs you out of Apple services, turns off the âFind Myâ and âActivation Lockâ security measures so that the system is no longer associated with you, and erases all your files, settings, apps and anything else. It deletes the encryption keys, permanently scrambling any data that remains.
If All Else Fails
If your PC or Mac is so old that it canât run a modern wipe process, you have one more option before seeking pro help. For Windows, several experts recommended the KillDisk app. The $49.95 Professional version runs from a USB drive and overwrites the ones and zeros that encode data on your hard drive with all zeros. Afterward, your computer will no longer boot into Windows unless you reinstall the OS.
For a Mac, your best option is a complex process that Apple describes online.
If these processes sound too complicated, or if your system wonât even turn on, use Appleâs recycling program for Macs or a disposal company that offers hard-drive destruction (or shredding) and recycling for consumers with either type of system. Look for ones that issue a certificate of destruction to verify the process. For instance, Ship âNâ Shred accepts drives or whole devices, with prices that include shipping ranging from around $30 to $200.
Modern technology leaves a lot of digital footprints, but at least you can sweep them off your old computer.
â Sean Captain is a Writer âď¸ in New York.
















