How to Wipe a Computer: 10 Things to Do

By: Patrick J. Kiger  | 
Before you sell or donate your used computer, how do you ensure the hard drive data is cleared?

When you're upgrading to a new computer, you might find yourself unsure what to do with your old one. Sure, you could sell it on eBay or Facebook Marketplace. But you need to know how to wipe a computer, so you can ensure that the sensitive data on your PC — financial records, passwords to credit card websites, important e-mails, and drunken pics from spring break — doesn't fall into the wrong hands.

While this can be intimidating, don't panic. In this article, we'll show you how to wipe a computer of personal information. With these vital tips, you'll be able to sell or donate your computer at factory default settings, giving you total peace of mind.


Personal Files Can Be Costly

Data thieves can use various programs to recover your sensitive files, even if you think you've deleted them. Just ask a British man who had to pay 100 pounds to a crook in Latvia to get back his old hard drive, after the crook mailed him a picture showing how he'd recovered his bank statements and a mortgage application. The man had been told earlier by a computer company that his faulty hard drive would be scrubbed when it was replaced [source: Arthur].

And this is not an isolated case. In 2009, British security researchers purchased 300 used computers from several countries and then perused the hard drives. They found that one-third of them still contained data from the former owners, including medical records from hospitals, proprietary business documents, and even test-launch information for ground-to-air missiles [source: Lamb].


10: Resell or Recycle?

Old computer monitors stacked up.
Don't throw out that old computer. It has a lot of materials that are hazardous in a landfill.

The first question is what to do with your old computer? If your PC or Mac is more than ten years old and unable to run the latest software, the answer is probably to recycle it.

Whatever you do, don't throw your computer away. It contains a lot of materials that are hazardous in a regular landfill, including heavy metals such as mercury, cadmium and lead [source: Tsydenova and Begtsson]. Also, many of the materials in computer parts can be extracted and reused to make new products, reducing the need to mine new materials. All you need to do is remove your computer's hard drive and take the other pieces to a local electronics recycling center.


If you have a newer computer, it would be better to sell or donate it. Decide whether to wipe the drive yourself or hire a professional to do the job. You can take your PC to one of Microsoft's certified refurbishers, who'll wipe it using state-of-the-art security methods.

For Mac computers, they can be shipped to Apple and you'll get credit at the Apple store if the company determines the computer has some monetary value [source: Apple]. However, if you're a reasonably tech-savvy person, read on to learn how to clean it yourself.

9: Back Up Data Onto a Portable Drive

SSD card for backing up your computer.
Backing up your data on a portable drive will give you an extra copy for emergencies as well as allow you to transfer your data to your new computer.

If you have a PC, before you do anything else, copy all the stuff you want to keep onto a portable drive and then recopy it onto the hard disk drive of your new computer. That way, you have an extra copy of your important data in case something goes wrong. You can also use a Microsoft utility called Windows Easy Transfer that lets you choose what you want to move over to your new machine, including documents, music, pictures, e-mail, system preferences, and user accounts. Use this utility along with a special cable to hook up your old and new PCs and transfer the data directly between them [sources: Microsoft].

Another option is to transfer files from your old PC onto a portable drive by attaching the drive to a USB port. You open both your hard drive and the portable drive in separate Windows Explorer windows and then click and drag your files and directories onto the portable drive. One advantage is that it also lets you do a little housekeeping and ditch stuff that you don't need anymore.


If you have a Mac, you don't need the portable drive, because you can transfer files directly from one machine to another using a FireWire or ThunderBolt cable connection. Use a program called Migration Assistant found in Applications/Utilities. Finally, data on both PCs and Macs can be transferred wirelessly if they are both on the same network.

8: Deactivate/Deauthorize Your Software

iTunes content seen on a MacBook and tablet.
To transfer your iTunes data, you have to deauthorize the program from your old computer and authorize it on your new one.

Back in the day — we're talking about the late 1980s and early 1990s — you could easily copy your old software programs (or somebody else's, if you didn't have strong feelings about software piracy) and reinstall them on your new PC. These days, however, software manufacturers are pretty strict about making sure that you've paid for every program that you use. That means you have to deactivate your programs and then transfer the licenses to your new computer.

Go through your old computer's software and make a list of the programs that you'll keep, and figure out the process for deactivating and transferring the programs. That can vary from manufacturer to manufacturer [source: Owen].


For Adobe Photoshop, for example, go to Creative Cloud, the company's online platform, and sign out of the program on your old PC. Then, install the software on your new machine and sign in [source: Adobe]. With iTunes, you actually have to deauthorize the copy of the software on your old machine, then sign in and authorize the program on your new machine before you can transfer your settings and iTunes purchases from Apple's cloud.

7: Destroy Your Drive or Reuse It?

Hard drive for a computer.
Make sure you replace your old hard drive with the same model.

As we mentioned, it's possible to dismantle a PC, take out the hard drive, and recycle the rest of the parts. But if you feel guilty about wasting the still-functional motherboard, memory chips, and intel processor in your old machine, you can pull out the old hard drive with your data and replace it with a blank refurbished hard drive on the cheap [source: Newegg].

Installing a new hard drive really isn't much more difficult than plugging and unplugging cables and turning a few screws. The key aspect of this setup process is to replace the old drive with one that's the same type.


6: Determine the Best Way to Destroy Your Drive

Hammer striking a computer hard drive.
Smashing your hard drive with a hammer will definitely destroy the data but there are more elaborate ways too.

There are differing opinions about how to best destroy computer hardware. Some suggest simply yanking out your hard drive, slipping on a pair of goggles for safety, and then smashing it several times with a hammer [source: Lamb].

Others recommend more elaborate measures — drilling holes or pounding nails through the drive; throwing it in a fire; cooking it in a microwave oven; or soaking it in diluted hydrochloric or muriatic acid. That all sounds a bit fiendish and can be hazardous to your health as well (acid baths give off toxic fumes).


A comparatively safer method involves disassembling the drive, removing the platters, and then sanding or grinding their surfaces to make them unreadable. You may have to invest $20 or so in a special set of screwdriver bits to remove the small screws that hold the drive's case in place, though you could also try a large flat-head screwdriver to pry it off [source: O'Reilly].

If you're a fan of the TV series "Breaking Bad," you may have seen the episode in which the characters park a powerful magnet next to a police evidence room to destroy incriminating data on a drive. In real life, that process, called degaussing, probably wouldn't work unless you had a really, really powerful magnet and focused its field very precisely [source: Lynn].

5: Have a Copy of the Operating System to Reinstall

Windows operating system on a computer.
If you don’t have your backup copy of your Windows operating system, you can get one from the Microsoft website.

Whether you're going to tear out your old drive and replace it, or wipe and reuse your old one, no computer will run without an operating system. If you have a Windows computer of a certain vintage, it probably came with a backup disk that you can use to reinstall the operating system after you've done your cleanup.

If not, third party tools can help you out. You can snag another copy from Microsoft via the Digital River website, and install it on a USB drive with at least 4 gigabytes of space, using the Windows 7/USB/DVD download tool. To activate the software, you'll need the Windows 7 product key, which should be on a sticker on your computer case.


If you've got a really old Mac, you'll need a disk with the operating system installation files as well. But if you've got a recent release such as Lion or Mountain Lion, you don't need one. Instead, after you erase the data on your drive, you can run a utility that will download the OS from Apple and reinstall it. We'll give you more detailed instructions later [source: Arndt].

4: Erase Your Data from the Hard Drive

Woman working on a desktop computer.
In addition to deleting your files, you should use a software program designed to wipe your hard drive clean.

Unfortunately, holding down the power button isn't enough for this job! Besides, you can't just rely upon deleting your files, because security experts say that stuff can be recovered by a sophisticated data thief. In fact, traces of data may remain, even if your repartition and reformat the drive.

That's why you should use one of the numerous software programs designed to obliterate your information, such as DBAN or Lavasoft File Shredder. The latter has the advantage of allowing you to wipe out sensitive data but leave other stuff that doesn't put you at risk [source: Lamb].


With a Mac, this process is easier. Just boot up your computer from the recovery partition by holding down the command and R keys as it restarts. Then open Disk Utility. Once in your disk utility sidebar and under the Erase tab's security options, choose 7-Pass Erase, which will overwrite your data seven times, obliterating it. This is going to take several hours, so bring along your tablet and read an e-book [source: Arndt].

3: Reformat the Hard Drive

Businessman working on a laptop computer.
Once you reformat your hard drive, all traces of old data are gone.

This is the step that's a little scary, because of its finality. Once you reformat a drive, you wipe clean the remaining traces of data, the software programs, and the operating system. On the other hand, that isn't necessarily a bad thing, because you're also going to undo any software problems and destroy any malware that's infected the PC. So eventually, once you reinstall a new copy of the operating system, it may run even better than before [source: Phelps].

The first step is to repartition your hard drive. If you have a Windows PC, you can do this by opening the Windows Control Panel and clicking System and Security, followed by Administrative Tools, and double-clicking on Computer Management. You'll probably have to provide the password for your main user account, the one with administrator privileges that allows you to alter the computer's settings.


Once you select Disk Utility, go to the Storage menu, and click Disk Management and then New Simple Volume. That will bring up a wizard program that will guide you through the rest of the process [source: Microsoft]. The process could take a few hours to complete.

2: Reinstall the Operating System

New Microsoft laptops in a store.
Use your Windows disk to reinstall the operating system on your PC; for a Mac, you can reinstall through Apple's cloud.

Normally, if you need to reinstall Windows because of a computer malfunction, you simply go to the Advanced Recovery Methods menu in Control Panel and then reconstruct the operating system from a recovery image that your manufacturer has installed in a separate partition on your drive. But remember that you've easily wiped all of that out. So you're going to need to use an installation disk. If you don't have the one that the computer came with, go to Microsoft for a copy and follow the onscreen instructions.

With a Mac running OS Lion or Mountain Lion, this is even easier. After you've completed erasing your data, quit Disk Utility, and make sure that you're still connected to the Internet. Then, in the Apple menu, choose the Reinstall OS X option, and Apple's cloud will do the rest. If you're running an earlier version of OS X, you'll need to put a backup system disk in the drive and click restart while holding down the C key [source: Arndt].

1: Make the Computer Shine

Woman using a special brush to clean computer keys.
You can use a special brush to get the dirt out of the keyboard or just give it a gentle shake and dust with a cloth.

OK, by this point, your old computer is at factory settings and you've taken care to ensure the security of your personal files. But while it might be clean on the inside, the next owner, assuming you have one lined up, isn't going to like getting a machine that's covered with fingerprints and pizza remnants.

So be considerate and give your old machine a good external cleaning, using a soft damp cloth and compressed air to get particles out from the crevices in your keyboard. If it's a desktop, you can also unscrew the door on the case and use the compressed air to clean out dust bunnies on the inside. For a laptop, carefully turn the machine upside down and gently shake out the crumbs and dust in the keyboard.

Finally, use a soft glasses cloth to wipe away smears and fingerprints from the screen. You'll feel better that you did [source: Asch].

Wipe Computer FAQ

How do you wipe a computer clean to sell it?
The first thing you need to do to wipe a computer is to backup all your data onto an external hard drive. To wipe your computer clean your first option is to take out the hard drive and either destroy it or reuse it. Another option is to use a software program to erase your data from the hard drive. Alternately, you can reformat your hard drive.
Is it okay to factory reset a laptop?
It is a good idea to factory reset your laptop, especially if it is having problems with the operating system. Factory resets allow you to fix large application errors or other OS issues. They also wipe out most malware and other unwanted programs that may have found their way into the system.
Is it possible to completely wipe a computer?
It is possible to completely wipe a computer. However, security experts say that sometimes data is still recoverable by a sophisticated hacker. Even if you repartition and reformat the drive, traces of data might be left behind.
Is it a good idea to wipe your computer?
It is a good idea to wipe your computer if you are planning to upgrade to a new system, or are selling or recycling an old computer. Wiping the computer not only gets rid of any malware, but also ensures that the sensitive data and personal information stored on your PC doesn't fall into the wrong hands.
What does it mean to wipe your computer?
Wiping your computer refers to making all data on a hard drive unreadable. Wiping is often used to remove data stored on a computer inaccessible before disposing of the device.

Lots More Information

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