Web Culture

4 Things You MUST Do When Selling or Giving Away Your Old Computer, Phone or Tablet

James Bruce 02-09-2012

how to clean computerHere’s a fun thing I like to do: buy an old hard drive on eBay, then run recovery software on it. It’s a little data treasure hunt, and you’ll be amazed at what you can find. Even more amazing though are people who don’t even bother to delete data first; they just sell the phone or throw away the machine as is. You might as well put family photos, bank documents and your passport in a box, then leave it outside your house with a giant “steal me” sign on it.


If you don’t want to be one of those thousands of people who fall prey to privacy invasions and identify theft every day, then read on. Here are 3 essential steps to take before getting rid of a device.


Even if you think you’ve copied everything you need, there’s probably something you’ve forgotten – your bookmarks, or application settings, for instance.

The best backup to is therefore a complete disk image of the computer you’ve selling or giving away. Use SuperDuper on a Mac, or read Tina’s excellent tutorial for Windows 5 Ways To Clone & Copy Your Hard Drive Read More .

For iOS devices, the computer you’re synced to would have automatically made backups. When you buy a new phone, you can simply restore your applications and purchases. To check if you’ve been backed up, connect the device to iTunes and open it up from the sidebar (you don’t even need it connected if you’re on the same network and latest versions); the Summary tab includes a Backup section as well as the last backup taken.

how to clean computer


Android devices vary greatly, but Ice Cream Sandwich version 4 and up automatically back up purchases and settings to your Google Play account. Check if this is working from the Android Devices section of your Google Dashboard. For older devices and the more intrepid hacker types, Titanium Backup (rooted only) is apparently the prefered method.

how to clean phone memory

Secure format

A lot of people know as much as delete their data first, but many don’t realise that deleted data can still be accessed using recovery software. That’s right, all I need to do is plug your drive into my computer, and click Go: the software will extract everything it can find, combining little bits into images files, documents, and music. You can buy this software for less than $100.

how to clean phone memory


This method of extracting data – even when it’s supposedly been deleted – works because “deleting” data doesn’t actually remove it from the drive – merely, it marks that area of the drive as available for use, and deletes the index of the file. The data itself – the 0s and 1s that make up that file, are still there.

This is where secure deletion comes in, in various levels of complexity. The basic principle is the same though: you need to write over the area of the disk where the file was stored. The most basic method is called “single pass” because it passes over the data and once and writes 0s all over it.

For most situations, a single pass is sufficient, but deeper recovery scans can still identify this data. For very sensitive data, multiple passes are required that not only zero out the data but also write random data over it a number of times. The US Department of Defence standard for securely erasing data specifies a whopping 7 passes; that is well and truly unrecoverable.

So, do you need elaborate and complicated systems to do this kind of secure formatting? Nope.


In OS X, head over to the Disk Utility and select the drive -> Erase tab -> Security Options.

how to clean phone memory

In Windows, you can use the command line DISKPART utility to “clean” a drive, securely formatting it.

Note that in both cases, you cannot securely erase the system drive, because that would be erasing itself; in this case, use a boot disk designed specifically to perform secure erases such as DBAN on PCs, or insert your OS X install CD and boot as if you were going to install a new system – Disk Utility is available from the Tools menu.


For Android devices, securely delete the SD card if you have one using the Windows method described above. Although there is a factory reset method built into Android OS, it is apparently not secure. For devices with a system partition, I suggest first enabling encryption from Settings -> Security -> Encrypt; then doing a factory reset. This is only available on Ice Cream Sandwich and above though, so you’ll need to search for a specific method if you’re running older versions of Android.

For an iOS device, data is automatically encrypted so recovery is incredibly difficult; go to Settings -> General -> Reset -> Erase all content and settings to effectively nuke everything before you sell it.

Re-install an OS

Depending on who the computer is intended for, reinstalling the OS is basic courtesy. Most brand name PCs and laptops come with restore CDs which will put your PC back to the way it was when you purchased it; use the license key that’s indicated on a sticker on the machine when prompted.

If you don’t have or can’t find these restore CDs, Linux is probably your best option; Ubuntu has a wealth of information out there – including a few of our own guides Getting Started With Linux and Ubuntu You're interested in switching to Linux... but where do you start? Is your PC compatible? Will your favorite apps work? Here's everything you need to know to get started with Linux. Read More , which a really nice person would download for the future owners and place on the desktop (hint, hint). You could of course just specify “no operating system supplied”, but some users will have no idea what this means and it may come back to bite you in the form of bad eBay ratings or unwanted phonecalls.

Whatever you do, don’t install something that you don’t have a license for. It could land you both in serious trouble when they take it for repair or phone up Microsoft to get support.

De-authorise DRM purchase

A lot of media comes with DRM 4 Ways to Copy iTunes Purchases From One Mac to Another [OSX] With music purchased from the iTunes Store, it's not always clear what you can or cannot do. This is largely due to the maze of DRM restrictions, and iTunes' design, which is obviously focused on... Read More nowadays; like iTunes. iTunes allows your own purchases to be downloaded to up to 5 of your devices; these can quickly add up though if you have a Mac, an iPad, iPhone and are regularly upgrading them.

Luckily, there’s a quick an easy way to deauthorize all your currently regisered devices at once – however, you can only do this once per year. To do this from iTunes, click on the iTunes Store from the left hand sidebar; then sign in to your account and view your account details. From there, you can select Manage Devices.

clear memory android tablet

(Oddly, I have 6 devices authroized right now; Apple maintains the maximum is 5, but perhaps this only applies to computers and not mobile devices)

You can also authorize and deauthorize a single machine from the iTunes Store menu on that machine. The iTunes account can only be changed once every 90 days though.

how to clean computer

Obviously, iTunes isn’t the only DRMed service out there, so check up on your own services to see if you need to deauthorize anything.

Do you have a checklist of things to do when selling or giving away a device? Let us know in the comments, and we shall be eternally grateful!

Image credit: ShutterStock: Computer Hacker

Affiliate Disclosure: By buying the products we recommend, you help keep the site alive. Read more.

Whatsapp Pinterest

Leave a Reply

Your email address will not be published. Required fields are marked *

  1. Raghav Gupta
    November 5, 2012 at 6:01 am

    thanks for the awesome tips

  2. Robert Gorman
    September 7, 2012 at 10:43 pm

    Always make sure that no personal Info is left on the old PC/laptop, by reinstalling the O/S and resetting it back to factory settings.

    If you don't have the original CD or recovery disk, borrow one and use your product Key on the side/bottom of your machine.

    • Bill
      September 11, 2012 at 9:06 pm

      I learned that I should have uninstalled Adobe Acrobat before getting rid of the HD. Uninstalling apparently tells Adobe that you want to reinstall it on another computer. I had already installed it on my work and home computer and that's all the installs they will allow.

  3. Saurabh Singh
    September 7, 2012 at 5:34 pm

    Thnx for the info.. i am planning to sell my old desktop pc.

  4. Marlene
    September 7, 2012 at 3:18 pm

    Love this - thanks!

  5. themainliner
    September 7, 2012 at 1:39 pm


    "For most situations, a single pass is sufficient, but deeper recovery scans can still identify this data. For very sensitive data, multiple passes are required that not only zero out the data but also write random data over it a number of times." - this is inaccurate. It is a widespread myth that a single pass is not effective.

    It is not necessary. It is only theoretically possible to restore data from a drive that has been covered with 0 and 1 in one pass. Modern hard drives are practical impossible to 'restore' after a single pass. No has succeeded, even in laboratory conditions, to retrieve data, even with a scanning electron microscope.

    Furthermore it's financially prohibitive to even try. There is taking sensible steps to secure your data and there is unnecessary expense. Secure Erasing fall into the latter category. It is not a case of being careful it is a case of not understanding the technical possibilities. DO NOT WASTE YOUR TIME AND MONEY!

    But don't take my word for it (Simon Slangen didn't); [Broken URL Removed]

    • muotechguy
      September 7, 2012 at 5:24 pm

      Given that you can do this for free, I'm not sure what you're shouting about.

      Wait, how do I know youre not the FBI trying to convince people not to wipe their data properly just so you can get at it more easily! AHA!

      • themainliner
        September 7, 2012 at 5:38 pm

        "You can buy this software for less than $100."

  6. Joshua L
    September 6, 2012 at 2:03 pm

    Great tips. The DRM one is something I wouldn't have considered. I try to have as little DRM content as possible, but I still have some.

  7. Mudit Warrior
    September 6, 2012 at 3:22 am

    Nice one James...good info

  8. Ellen Odza
    September 6, 2012 at 2:23 am

    My BF bought a new phone and had Best Buy transfer everything over before giving them her old phone as a trade-in. She later discovered they'd not transferred her photos over properly and she had no backup. Over a hundred photos of the grandkids - gone forever. BACKUP IS GOOD!

  9. Joel Alar
    September 6, 2012 at 1:54 am

    as a best practice, we use a data disposal software to surely wipe all the data inside the harddrive for data securitty and confidentiality.

  10. Rishabh Arora
    September 5, 2012 at 3:32 pm

    Very useful. Thanks :)

  11. Praveen pandey
    September 5, 2012 at 10:06 am

    nice set of info.

  12. Greg Underwood
    September 4, 2012 at 6:59 pm

    I have used Hard Disk Eraser program with good results. A friend recommended it.

  13. Therence Davids
    September 4, 2012 at 2:44 pm

    Great information, thank you!

  14. Steve
    September 4, 2012 at 2:16 pm

    You should also add "Digital Copier" to the list of devices you need to do these steps on, Most digital copiers place an electronic copy of every document scanned for copying to an internal hard drive. There was a news story on about how people don't think about it, but everyone makes a copy of tax returns or tax documents, Employers copy Drivers license and Social Security Cards for employment files, all kinds of stuff gets copied and you don't even think about it.

    • James Bruce
      September 4, 2012 at 2:26 pm

      Great point Steve, I imagine this process varies by model.

  15. danny elder
    September 4, 2012 at 2:31 am

    I picked up an old Gateway Pentium 4 that I am actually using now,out of the garbage by my house. It had everything left on here from the previous owner Including business records and a list of drug screen reuls complete with SSN's ,names phone numbers and everything! There is no telling what all is on here. I'm not real pc saavy so there could be stuff I haven't found yet.

  16. Greg
    September 3, 2012 at 6:03 pm

    I'm selling my laptop on Ebay, 2nd time, and you mentioned about putting Linux on it, I won't do that this time since hardly anyone knows what that is, I'll put Vista back on (sadly :( and for deleting everything on hard drive, I use "Darik's Boot And Nuke" cd"

  17. GrrGrrr
    September 3, 2012 at 4:52 pm

    useful tips.

    btw- there r lot of good FREE Secure format software's. not sure u specifically mentioned a name for a paid software

  18. Bren Herring
    September 3, 2012 at 3:29 pm

    Been saying this for years! :)

  19. gpvprasad
    September 3, 2012 at 12:11 pm

    Most of them look like for Apple not for other computers.

    • James Bruce
      September 3, 2012 at 3:09 pm

      None of these are apple specific and all include instructions for other machines.

  20. Pilgrim57
    September 3, 2012 at 11:43 am

    I found a 250GB external drive by the bins in my building. Plugged it in worked fine.
    Had iTunes library, resume, personal correspondence & job applications still on it!
    Used diskpart on a usb stick, useful to know I can use it on hdd's.
    A drive failed on me out of warranty so took a hammer to it:)

    • Michael Hart
      September 3, 2012 at 7:33 pm

      Strong magnets are far easier and much more fun (afterwards) ;)

      • Joshua L
        September 6, 2012 at 2:06 pm

        I also like taking a drill to my old ones.

    • Gino Louie Peña
      September 7, 2012 at 6:56 am

      Go Green!, we assume that you sell or gave it to the junk shop ;-)

  21. moez
    September 3, 2012 at 11:13 am

    these tips are just for windows/Mac/Android/iOS users but not for linux users.
    i'm using ubuntu. for the second tip. what should i do? (i'm using ext4 fs)
    i mean, should i use an app to delete/change the data of deleted files or ext4/linux delete/change the data when i delete the files?

    • James Bruce
      September 3, 2012 at 3:11 pm

      The boot CD mentioned will work for Windows or Linux drives; or you can use the shred command from within ubuntu: (can only point you in the right direction though I'm afraid)

  22. Usman Mubashir
    September 3, 2012 at 10:20 am

    What I do is a complete re-install of windows using full formatted drives even if it takes a whole day. then make sure of the deleted data by using software.

    • Michael Hart
      September 3, 2012 at 7:32 pm

      A reformat isn't going to securely over-write the actual data on the drive, as the OS is only a tiny fraction of the entire disks capacity. You should use software to write random data multiple times over the entire disk.

    • Gino Louie Peña
      September 7, 2012 at 6:54 am

      as mentioned in the article or blog use DBAN it is a free softare that will securely wipe out your data, see more information in their website http://www.dban.org/

  23. Tug Ricks
    September 3, 2012 at 10:16 am

    So if my laptop didn't come with restore CD's when I bought it, is there any possible way to reinstall Windows after a HD wipe, or is Linux my only option? Any way to order those from MS if I have my serial key?

    • Kory
      September 3, 2012 at 4:59 pm

      once you wipe your Hard Disk its unrecoverable. If you have a windows serial all you need is a windows install disk which you can find a download for

  24. Ahmed Khalil
    September 3, 2012 at 6:13 am

    Thanks for these notes

  25. Mani Ahmed
    September 3, 2012 at 5:16 am

    If one is a novice then the head of this article might be misconstrued ... because they would / might only end up doing this ... where as the backup itself is a huge discussion ... favourites of chrome, internet explorer. the contact list, the pictures in my documents and other such folders are those which a novice user normally misses while taking a backup of a windows system.

    However for a mac user and an advance user the article is indeed very good, the DRM is something which it even a point to remember for myself.

    Thanks and keep up the good work!

  26. rama moorthy
    September 3, 2012 at 4:13 am

    Nice tips ..!

  27. Rich Mc.
    September 3, 2012 at 3:58 am

    My sister decided to sell her old laptop last year and even though I ahve always told her to either remove the hdd or wipe it clean she didn't and a few weeks later had her bank account broken into....It was a hard lesson to learn but one she will never forget.

    • muotechguy
      September 3, 2012 at 7:29 am

      Wow, sorry to hear that. Still, lesson learnt I guess.

  28. IamAshMcLean
    September 3, 2012 at 2:49 am

    Big Mistake selling a computer without backup... the last time i purchase a phone, comes with XXX on it... very embarassing moment for the seller... :/

  29. John B Lontz
    September 3, 2012 at 2:46 am

    Great information, thank you!

  30. Paul Harris
    September 3, 2012 at 2:44 am

    When my old laptop died.....some sort of internal bios? crash, I removed the old HD , purchased an enclosure for it and plugged it in a USB port. I removed all the data, etc. that I wanted, reformatted it and now use it for a backup drive.

    The case for the HD was less than $20 at Staples.

  31. bob g
    September 3, 2012 at 12:15 am

    Good tips.