Completely Erase a Hard Drive

Category: Hard-Drives

When you replace a hard drive, what do you do with the old one? Most people give their surplus drives away to friends or charities. Some just throw them in the trash. But what about all the data on that old drive? Even if you deleted files or formatted the drive, your data might still be readable. Here's how to securely and completely erase every last bit of data from your hard drive…

How to Erase Your Hard Drive

What's on that old hard drive? Your name, address, phone number, email, tax returns, bank account info, love letters... maybe some software or (ahem) other files you'd rather no one else knew you had. Maybe your family's info is on there, as well. How can you erase all that stuff before disposing of the drive?

You might be surprised to learn that when you delete a file, it's really not gone. All the "delete" command does is erase the record of a file's location on the hard drive, stored in the Master File Table (MFT) or File Allocation Table (FAT). That's like removing the cards from a library's card catalog but leaving the books on the shelves for anyone to inspect at random.

Okay, but formatting a hard drive erases all data on it, right? The operating system warns you about that before it executes the format command. But no, you can even recover files from a freshly formatted drive if nothing has been written over them. Data recovery software such as the Data Recovery Wizard from can easily restore files on a freshly formatted drive.
Erase Hard Drive

To truly make your sensitive data unreadable, you have to cover it completely with new data; not just once, but several times. It's like using a pen to scratch out something you wrote earlier. A few penstrokes will obliterate old writing to the casual observer, but someone with a magnifying glass and determination can still make out the indentations of the old writing on the paper unless you scribble over it half a dozen times or more.

Tools to Securely Erase Files From a Hard Drive

Mac operating systems come with secure data erasure built in. All you need to do is move folders or files to the trash can and from the Finder menu select 'Secure Empty Trash'. Windows does not have a secure data erasure function, but several third-party utilities provide this ability.

Eraser is a free utility for securely erasing data from a Windows hard drive. It works with Windws 95/98, XP, Windows Server 2003 and 2008, Vista, and Windows 7. Eraser has a simple name but it erases files completely in several complex ways.

The default erasure method used by Eraser and many other similar programs is called the Guttmann Method after its inventor, Dan Guttmann. It overwrites data 35 times, ensuring that no one will be able to recover it. Of course, that takes a very long time. Eraser and other utilities let you schedule a secure data erasure during hours when you won't be using your computer.

A second, less thorough method is called the US DoD 5220-22.M Method. This is a standard developed by the U. S. military for securely erasing drives "good enough for government purposes." It overwrites data seven times. That will thwart all but the most determined and well-equipped data recovery experts, but it won't stop the "men in black" from the CIA, the National Security Agency, or those guys from CSI.

Years ago, I remember reading a story about one paranoid guy who lived in fear of the feds busting his door down and confiscating his computer. He had a strong electromagnet positioned near the computer, so that when the dreaded midnight raid occurred, he could flip a switch and instantly wipe the hard drives clean. I wouldn't recommend that method, because forensic tests have shown that electromagnets can leave some data intact.

I'd like to mention one final method of completely erasing your hard drive, which I have personally found to be immensely satisfying. It involves physically removing the hard drive from the system unit, and beating it senseless with a 16-lb steel sledge hammer. There's always the possibility of shrapnel, so place the drive in a brown paper grocery bag first, and wear eye protection. When you're finished, you can inspect the carnage and maybe learn a little something about how hard drives work.

Got something to say about erasing a hard drive? Post your comment or question below...

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Most recent comments on "Completely Erase a Hard Drive"

(See all 30 comments for this article.)

Posted by:

20 Nov 2009

See (, so put the drive into a USB or firewire external drive enclosure of your choice and hook it to a linux box and run
"dd if=/dev/zero of=/dev/hdX" on it.
Ignore all the "DoD recommendation" b.s.

A single wipe will suffice, the issue is that it may be interrupted and may not wipe all the sectors, so if you fear that a power failure will cause an incomplete erasure then anything that uses the "secure erase" (SE) feature of the ATA command set will cause that the wipe process be continued even if the drive is powered down and moved to another host.
See (

Keep the tin hat on!

Posted by:

21 Nov 2009

Leon Dombrosky:
You said, "16 pounds of Satisfaction! Do the Rolling Stones know this yet?"

Leon, you forgot Tennessee Ernie Ford. He owns the first half of that title.

Posted by:

munsif ali from pakistan
22 Nov 2009

even after formatting a hard disk while making fresh installation of windows, the data is still not lost from previous installation.

I guess, That unerased data from previous installation and work , can interefere into windows installation process , if anybody has comments , kindly inform at

Posted by:

24 Nov 2009

I've taken to using the built-in hd secure erase function. From what I've read even the 'black/white hat' guys are unable to recover data after it's been run on a drive. If anyone has info that disputes this I'd love to see it.

Posted by:

Dalton Tamney
24 Nov 2009

I used to volunteer for an organization that refurbished older computers for schools. Our technique for making sure hard drive were erased was just like yours, a heavy hammer with the hard drive set on the steel side of our forklift. Worked like a charm with the added benefit of being able to take out some frustrations.

Posted by:

24 Nov 2009

The computer failures (my own as well as "client's") have been due to failure of a hard drive. If they have sufficient back up, disassembly is the best security; the platters make an excellent "wind chime" hung with fishing line to ensure they retain their valuable and totally secure information.

Posted by:

24 Nov 2009

Run whatever software you think will remove the data. THEN Disassemble the drive and remove the platters. Run a strong magnet back and forth in contact with the platter surface on both sides. Then use an icepick to score the surface of each side in a quarter-inch crosshatched pattern - deep, nasty, curly-edged gouges from edge to edge. Fold the platter in half and beat it flat with a hammer - both sides. Fold it in half again and beat it down again. This process should inflict enough physical damage to preclude anyone, including space-aliens, from getting much (if anything) from the platter. The ultimate step is to incinerate/melt the platter.

Posted by:

24 Nov 2009

dd if=/dev/urandom of=/dev/sdX would be safer. And

dd if=/dev/random of=/dev/sdX

even more so. But /dev/random is very time consuming, unless you have special hardware for „white noise“ generation.

My plan for information destruction:

1. boot up PC with LiveCD.

2. delete disc completely

3. format HDD

4. cript it with GnuPG taking very long password (say, 1000 symbols generated with /dev/random)

5. repeat steps 2 and 3.

6. done

Repeating it several times would be even safer. But I'm not sure it would be worth it. It is possible to script the batch and leave it for whole night.

EDITOR'S NOTE: Or... beat it with a hammer. :-)

Posted by:

24 Nov 2009

There is a great program here:

Simple live CD

Posted by:

C Chad
24 Nov 2009

Try WIPE a very old little piece of software that fits on a floppy from IBM. The documentation states that it will rewrite up to 8Gb, but it will rewrite drives of 250Gb, I suspect it will successfully rewrite larger drives as well. I've been using and testing WIPE for several years the only data I've been able to recover is none!

Posted by:

24 Nov 2009

Boring but effective way: DBAN

More exciting, less work than hammer: meltdown with cutting torch (or the propane forge)

My favorite and (of course) the most dangerous: thermite

Posted by:

24 Nov 2009

You might also try one of these two ways:

NIST has a guide for media sanitization at

And while I'm sure a 16lb sledge hammer is quite nice, I prefer .40 caliber at 7 yards or .308 caliber at 100m.

Posted by:

25 Nov 2009

IBM created a utility called Secure Data Disposal (SDD)which is freely available now from Lenovo. It runs from a self-booting CD and is operating system independent.

Posted by:

27 Nov 2009

I tried ERASER a few months ago and there was trouble with the latest version which promised to unbug this:

The software caused my computer to hang; to freeze up. I see it was updated July 2009. Nothing new since then.

I definitely plan to use it once the bug is resolved. So in the meantime I have been using File Shredder at
[I highly recommend this as it NOT only permanently deletes files (using wiping up to 35 times) but you can also wipe the Free Space on your computer using the Guttmann Method.

Also: I Love Your Newsletter, Bob.
Believe me you have saved me an inordinate amount of money with your Recommendations on free(Quality) software.

I really Appreciate it!


Brooklyn, NY USA

Posted by:

28 Nov 2009

I like to take a drill to my platters as well. Good article and good advice. Though I don't think a paper bag will hold up too well to a sledge hammer.

Posted by:

22 Jan 2010

Tenderize thoroughly with hammer. Add 2 cups of water containing a 1/3 cup of salt. Allow to air dry for three day. Serves no one.

Posted by:

Nancy Johnson
12 Feb 2010

Nice article.I have learnt a lot from it. But I have used Wipe Mac software and got very satisfying results. Why don't you try this tool, it is also very nice.

Posted by:

05 Feb 2013

Can someone tell me if using Erase will get rid of everything... including the OS and any software loaded on the machine or just the files for said software? I am looking to give my old PC to my sister and wanted to keep the OS Windows XP and also MS Office Suite in tact for her... can that be done with Erase? Please advise.

Posted by:

17 Apr 2014

How about throwing the hard drive or USB key in a fire and burning them?

Posted by:

Paul from NJ
28 Feb 2016

I am going to use the Website where Not only do I Permanently Delete Files etc., but; where I Free Up Space on my Hard Drive.

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