How to erase an old hard drive before giving it away

An executive asks: I need to erase my old hard drive before I give my old PC to a friend. What is the best way to do this?

Of course, the best way is to have a qualified IT security professional do this for you. Still, if you want to do it yourself, here is an answer:

For this step especially, having the help of a qualified IT professional is important. If you choose to do it on your own, realizing that this isn’t as secure as totally destroying all the data on the hard drive it provides some good security and is easier to accomplish on your own, I suggest these steps:

a) Use Windows Explorer to delete all your files that you know of from the computer. This really doesn’t delete the files from someone who is very interested in getting your data, but it helps. Optionally, you can go ahead and use SDelete as described in step c to delete the files and/or overwrite them with several passes to scour them from the drive (see below).

b) Run the “Reset the computer to factory conditions” CD that originally came with your laptop. This installs the operating system to “factory new” conditions for the person you are giving the laptop to.

c) Go to (you’ll be redirected to a Microsoft page) and download the file utility called SDelete. Unzip the file and then review the license terms. Then run SDelete from a DOS prompt using the -z parameter to overwrite any unused space to destroy the data that is “erased” but not erased. You can choose the number of passes based on how much time you have. The first pass is crucial and that will run fastest. So, the command line entry at the C:>  prompt is:

SDelete -c

If you want more passes, and are willing to wait, you can use

SDelete -p 5 -c

Substitute a different number besides 5 if you want a different number of passes. Remember that the files the “new installation of Windows” only overwrote with one pass as SDelete with the -z parameter is only overwriting free space. If you have more than one partition, you’ll want to be sure they are all cleaned.

d) Do your friend a favor if you want to and go to and choose “security and updates” and run “Microsoft Update” in “Express” Mode until there are no more patches.


  • Mike Foster May 10, 2010 at 1:51 pm - Reply

    I was just contacted by a client that has 300 drives now and will have another 600 drives soon to destroy. They are not interested in ever “giving away” the hard drives and need the data destroyed. For such a large number of drives, a degaussing machine that destroys the information or some kind of press that physically destroys the drive is preferable. Furthermore, the destruction device will need to process the drives quickly or take them in “batches” so the process of destroying the data on 900 drives can be accomplished in a reasonable amount of time.

  • Alan Osborne September 20, 2010 at 11:53 pm - Reply

    An excellent (and free) utility to securely erase a hard drive’s content is Darik’s Boot and Nuke (DBAN): (Review of DBAN)

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