How to Safely Erase Your Computer: A Complete Guide

Upgrading to a new computer and not sure what to do with the old one? You might consider selling it on eBay or Facebook Marketplace. But first, learn how to wipe your computer properly to make sure sensitive information — like financial details, passwords, important emails, or those embarrassing spring break photos — doesn't get into the wrong hands.

Though it may seem overwhelming, don't stress. This guide will show you exactly how to wipe your computer clean of personal information. With these essential steps, you'll be able to sell or donate your device, restoring it to its factory settings and ensuring your privacy is protected.

Personal Information Can Be Expensive

Data thieves have the ability to use various software tools to recover your sensitive files, even if you think they've been deleted. Take, for example, a British man who had to pay 100 pounds to a criminal in Latvia to retrieve his old hard drive after the thief sent him a photo showing how he had recovered his bank statements and mortgage application. The man had previously been assured by a computer company that his faulty hard drive would be wiped before being replaced [source: Arthur].

This isn't an isolated incident. In 2009, British security researchers bought 300 second-hand computers from multiple countries and examined their hard drives. They discovered that one-third still contained personal data from the previous owners, such as medical records, confidential business documents, and even test-launch data for ground-to-air missiles [source: Lamb].

10: Should You Resell or Recycle?

The first thing you need to decide is what to do with your old computer. If your PC or Mac is over ten years old and can't handle the latest software, the most likely answer is to recycle it.

Whatever you choose, never toss your computer in the trash. It contains hazardous materials that are harmful in a typical landfill, including dangerous metals like mercury, cadmium, and lead [source: Tsydenova and Begtsson]. Additionally, many parts of the computer can be recovered and reused, which helps reduce the need for new resources. Simply remove the hard drive and take the remaining components to an electronics recycling center.

If your computer is relatively new, it’s a better idea to either sell or donate it. You can choose to wipe the hard drive yourself or hire a professional for the job. Microsoft's certified refurbishers offer a service where they will wipe the drive using advanced security methods.

For Mac computers, you can send them to Apple for evaluation, and if the company determines the device has value, you can receive store credit [source: Apple]. However, if you have some technical know-how, you can follow the steps to wipe it yourself.

9: Transfer Data to a Portable Drive

If you’re using a PC, the first step is to copy all your important files to a portable drive, then transfer them to your new computer's hard drive. This way, you’ll always have an extra copy of your critical data in case something goes wrong. Microsoft offers a utility called Windows Easy Transfer that helps you move your documents, music, pictures, emails, system settings, and user accounts to your new PC. Using a special cable, you can connect the two PCs and transfer the files directly [sources: Microsoft].

Alternatively, you can transfer files from your old PC to a portable drive by connecting it to a USB port. Open both the hard drive and portable drive in separate Windows Explorer windows, then drag and drop your files into the portable drive. This method also lets you clean up by deleting unnecessary files.

If you have a Mac, you don’t need a portable drive. You can directly transfer files from one Mac to another using a FireWire or ThunderBolt cable connection. Use the Migration Assistant program located in Applications/Utilities. Finally, you can wirelessly transfer data between PCs and Macs, provided both devices are on the same network.

8: Deactivate/Deauthorize Your Software

In the past — specifically the late 1980s and early 1990s — it was easy to copy your software programs (or someone else's, if you were unconcerned with software piracy) and install them on a new PC. Nowadays, however, software companies are much more diligent in ensuring that you’ve properly paid for each program you use. This means you’ll need to deactivate your programs and transfer the licenses to your new machine.

Go through the software on your old computer and create a list of the programs you wish to keep. Then, figure out how to deactivate and transfer those programs, as the process can differ by manufacturer [source: Owen].

For instance, with Adobe Photoshop, log into Creative Cloud, Adobe's online service, and sign out of the program on your old PC. Then, install it on your new computer and sign back in [source: Adobe]. For iTunes, you need to deauthorize the software on your old computer, sign in on the new one, and authorize the program before transferring your settings and iTunes purchases from Apple's cloud.

7: Destroy Your Drive or Reuse It?

As previously mentioned, it’s possible to dismantle a PC, remove the hard drive, and recycle the remaining parts. However, if you feel wasteful about throwing away a still-functional motherboard, memory chips, and Intel processor, you can remove the old hard drive with your data and replace it with an inexpensive refurbished one [source: Newegg].

Installing a new hard drive is not much more challenging than connecting and disconnecting cables, along with tightening a few screws. The key part of this process is ensuring you replace the old drive with one of the same type.

6: Determine the Best Way to Destroy Your Drive

There are various suggestions for destroying computer hardware. Some people recommend simply removing your hard drive, putting on safety goggles, and smashing it a few times with a hammer [source: Lamb].

Some suggest more extreme methods, such as drilling holes or driving nails through the hard drive; tossing it into a fire; microwaving it; or immersing it in diluted hydrochloric or muriatic acid. These actions can be quite dangerous to your health, as acid baths release toxic fumes.

A relatively safer approach involves taking apart the drive, removing the platters, and then sanding or grinding their surfaces until they are unreadable. You may need to spend around $20 on a special set of screwdriver bits to remove the tiny screws securing the drive's case, or you can use a large flat-head screwdriver to pry it open [source: O'Reilly].

If you're a fan of the TV series 'Breaking Bad,' you might recall the scene where characters use a powerful magnet near a police evidence room to destroy data on a drive. In reality, this process, known as degaussing, likely wouldn't work unless you had an exceptionally strong magnet and were able to direct its field with great precision [source: Lynn].

5: Have a Copy of the Operating System to Reinstall

Whether you're replacing your old drive or wiping and reusing it, no computer can function without an operating system. If you have an older Windows computer, it likely came with a backup disk that you can use to reinstall the OS after you’ve cleaned up the system.

If you don’t have a backup disk, third-party tools can assist you. You can download another copy of Windows from Microsoft via the Digital River website, and use the Windows 7/USB/DVD download tool to install it on a USB drive with at least 4GB of space. You’ll need the Windows 7 product key, which should be on a sticker on your computer’s case, to activate the software.

For older Mac computers, you’ll need a disk containing the OS installation files. However, if you have a recent version, such as Lion or Mountain Lion, you don’t need one. Instead, after erasing the data on your drive, you can run a utility to download the OS directly from Apple and reinstall it. We’ll provide more detailed instructions later [source: Arndt].

4: Erase Your Data from the Hard Drive

Unfortunately, holding down the power button won’t be sufficient! Simply deleting your files isn’t enough either, as security experts warn that sophisticated hackers can recover deleted files. Even after repartitioning or reformatting the drive, traces of data could still remain.

That’s why it’s recommended to use software designed to completely erase your data, such as DBAN or Lavasoft File Shredder. The advantage of the latter is that it allows you to destroy sensitive information while leaving less critical data intact [source: Lamb].

For Mac users, the process is more straightforward. Simply boot your computer from the recovery partition by holding down the command and R keys during restart. Then open Disk Utility. In the sidebar under the Erase tab, select the 7-Pass Erase option, which will overwrite your data seven times to ensure it’s fully erased. This process can take hours, so you might want to grab a tablet and enjoy an e-book during the wait [source: Arndt].

3: Reformat the Hard Drive

This step can feel a bit daunting because it erases everything on the drive. By reformatting, you get rid of all data, software, and even the operating system. But don’t worry—this also eliminates any issues like software glitches and malware, potentially making your computer run better once you install a fresh operating system [source: Phelps].

To start, you need to repartition your hard drive. On a Windows computer, open the Control Panel, select System and Security, then Administrative Tools, and double-click Computer Management. You’ll likely need to enter the password for the account with administrator privileges in order to make these changes.

After selecting Disk Utility, head over to the Storage menu, click on Disk Management, and then choose New Simple Volume. A wizard will appear to guide you through the remainder of the setup process [source: Microsoft]. This operation could take several hours.

2: Reinstall the Operating System

Typically, to reinstall Windows after a malfunction, you'd access the Advanced Recovery Methods menu in Control Panel and restore the operating system from a recovery partition created by the manufacturer. However, since you've erased that partition, you’ll need an installation disk. If you don't have the original disk, visit Microsoft to get a new one and follow the instructions provided.

For Macs running OS Lion or Mountain Lion, this process is even simpler. Once you've erased your data, close Disk Utility, and ensure you're connected to the Internet. Then, from the Apple menu, select the Reinstall OS X option, and Apple's cloud service will handle everything for you. If you're using an older OS X version, insert a system backup disk into your drive, and restart while holding down the C key [source: Arndt].

1: Make the Computer Shine

By this point, your old computer is back to its factory settings, and you've ensured that your personal information is secure. However, even though the interior is spotless, the next owner—if you’ve arranged for one—might not appreciate receiving a machine covered with fingerprints and pizza crumbs.

Be thoughtful and give your old computer a proper exterior clean. Use a soft damp cloth and compressed air to clear dust from the keyboard crevices. If you're working with a desktop, you can remove the case door and use compressed air to remove any dust bunnies from the inside. For a laptop, flip it over carefully and gently shake out any crumbs or dust from the keyboard.

Lastly, use a soft glasses cloth to wipe away any smudges or fingerprints on the screen. You'll feel much better knowing you did [source: Asch].