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How should I erase my hard drive before I give it away?

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Summary: Erasing your hard drive before you give it away is important. Exactly how thorough an erase you need depends on your data and level of paranoia.

I would like to clear off/erase all the programs on my hard drive and clean it up so that it's available for donation. What's the best/simplest way to do this?

To begin with, good on you, not only for your donation but for thinking to do this. All too frequently we hear of computers donated by banks, hospitals, or other institutions turning up with all sorts of private information that should have been erased first.

The best way? Well ... how paranoid are you?

Conventional wisdom is that reformatting your disk is the right thing to do. And I agree with that, if done properly.

What do I mean by "properly"?

Windows (all versions), and even MS-DOS before it, has the option to perform what's called a "quick format". In reality, a quick format does very little except create an empty root directory on the hard disk and possibly add a label. The rest of the disk is actually assumed to be properly formatted already and left alone. That's why it's quick.

And that's why it's insecure. Since the rest of the disk is left untouched, any data that may already have been there will remain. Many commonly available disk recovery tools will be able to recover data from a "quick" formatted disk.

"Well ... how paranoid are you?"

So the basic and common answer is to reformat the disk, making sure to specify unconditional format. Depending on the version of Windows or MS-DOS you have, that's typically a FORMAT /U at the command line, or making sure that Perform a Quick Format is not checked when using disk management tools.

And that's my general recommendation.

But... here's where paranoia sets in.

It's theoretically possible to recover data even after a disk has been unconditionally formatted. It's not easy and may require special tools (both hardware and software). In general it's a very expensive process. But it may be possible.

It's a common recommendation to use a big heavy magnet to really erase a hard disk. My advice: forget it. Any magnets you're likely to have around the house, even your big speaker magnets, are unlikely to affect your hard disk in any significant way.

An alternate approach is to do that unconditional format several times. Not a bad idea, and if you can I'd also alternate file system types, allocation sizes, and whatever other parameters you have control over between successive formats. It's not bullet-proof, but it will make that difficult potential recovery even more difficult.

But to really, positively, and permanently destroy your data you need to physically destroy the disk. Personally, if I care enough to go this far I use a drill press and drill a few holes all the way through the hard drive casing, through the disk platters, and out the other side. (OK, ok ... even then it's possible for some data recovery by a seriously dedicated, and seriously well financed, expert ... but it's very much like taking a bucket of shredded documents and trying to put them back together - one heck of a lot of work.)

Unfortunately, that level of destruction also makes your gift significantly less useful.

I'd stick with reformatting.

A version of this article that can be republished without cost is available at ArticlesByLeo.com (terms).

Article C2247 - December 26, 2004

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Recent Comments
70 Comments

Just write zeros to the disk. Takes a long time but it's worth it, WD has a utilty that can accomplish this. http://support.wdc.com/product/download.asp?groupid=609&sid=3&lang=en

Posted by: Tommy Lewis at May 12, 2010 1:51 PM

i have a laptop that the screen is broken on. i want to erase the hard drive, but cant see anything to do it. i used to work at a drs office that has an MRI, if i have them put it in the room while its one will it do the trick? if so, how long should it be in there and how close? thanx!

I think you risk damaging the MRI (there's a reason they say NO METAL). I'd remove the drive and perhaps use another machine to wipe it.
Leo
22-May-2010

Posted by: Patti at May 21, 2010 6:46 PM

Long-time fan, first time caller . ..

If you are looking to erase and recycle your laptop, we offer a free and secure service at www.EraseMyLaptop.com

Please support our goal of keeping laptops and smartphones out of landfills. Our goal is to be sure your personal information is completely erased in the process.

Thanks for the great article and many years of excellent computer advice Leo, you are a legend!

Posted by: Seth Brown at June 15, 2010 7:29 PM

Yeah it is very imp to delete all the sensitive data b4 u get rid of ur hard drive.The simplest way to do this is by formattng the drive...but that too may not delete all the data and there are always chances to recover them.I can suggest you 1 tool that will remove all ur data permanently forever and no other tool can also be able to recover it.Advanced System Optimizer...there is this tool named Secure Delete in ASO that does the permanent deletion of the data...but be cautious once the data removed can not be recovered anyhow.
its free version is also available at cnet

Posted by: james kingston at July 19, 2010 2:09 AM

I had reformatted a hard drive for someone and reinstalled windows xp. Then my friend tells me his wife wanted music and pictures on it. I could not retrieve them. So, after some researching I bought a program for $70.00 called Power Data Recovery that retrieved all formatted data to an external hard drive as long as the original data was not rewritten over. I was able to retrieve all her pictures and music. Then I burned them all to 2 DVD's for her (or it would have been like 6 cdr's). So,yes, it is possible with the right tools to retrieve data unless it is completely rewritten over with a data destroying program.

Posted by: Chris Hansen at July 20, 2010 1:10 PM

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