# Selling my computer -- how do I completely wipe the hard drive? **URL:** \ **Category:** Factual Questions\ **Created:** [June 5, 2008, 9:02am UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857 "2008-06-05T09:02:16Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Red\_Barchetta](https://avatars.discourse-cdn.com/v4/letter/r/da6949/32.png) [@Red\_Barchetta](https://boards.straightdope.com/u/Red_Barchetta)\ **Post date:** [June 5, 2008, 9:02am UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/1 "2008-06-05T09:02:16Z")
So I want to sell my computer, but I also want to ensure none of the files on it can be accessed. I already restored it to factory condition, but it’s to my understanding that data can still be recovered via a recovery program of some sort until the data is actually overwritten. I know there are programs available that will wipe the entire drive, but does that include the OS as well? If so, that’s a problem. Since I no longer have the restore CDs for my computer, I have to use the “restore” option that Sony pre-installed on the computer itself anytime I want to restore it. Which is fine, except I have no means of reinstalling Windows XP if it does get deleted. So are there any (free) programs that will wipe file data from my computer, but leave Windows alone? ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [June 5, 2008, 9:19am UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/2 "2008-06-05T09:19:06Z")
The last time I was in a situation like that, I wrote a little program that wrote random data to an output file. I let it run until the output file had consumed all of the free space on the disk, and then deleted the file. It wouldn’t meet NSA standards for eradicating every last scrap of old data, but it was good enough for my needs. If the data is really sensitive, physical destruction of the disk drive is the only way to guarantee that the data can’t be recovered. ---
**Author:** ![NineToTheSky](https://avatars.discourse-cdn.com/v4/letter/n/b5a626/32.png) [@NineToTheSky](https://boards.straightdope.com/u/NineToTheSky)\ **Post date:** [June 5, 2008, 10:54am UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/3 "2008-06-05T10:54:31Z")
There are plenty of free programs that will overwrite your hard disk with random data - which is the most secure way short of physical destruction. Some are approved by the US military. This will erase everything on your HD, including the OS. I don’t know how Sony go about things, but normally the OS is stored on a separate partition and can be transferred to a bootable CD that allows you to restore your OS and relevant drivers. If there is no option to do that, then the only other option is to ask Sony to supply the recovery CDs. They may charge you for this. ---
**Author:** ![GSV\_Consolation\_of\_Dreams](https://avatars.discourse-cdn.com/v4/letter/g/f1d935/32.png) [@GSV\_Consolation\_of\_Dreams](https://boards.straightdope.com/u/GSV_Consolation_of_Dreams)\ **Post date:** [June 5, 2008, 10:59am UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/4 "2008-06-05T10:59:24Z")
The restore files SHOULD be in a separate partition on your hard drive. I’ve used [Darik’s Boot and Nuke](http://dban.sourceforge.net/) several times before without any problems. It’s free, open source and simple to use. You can specify which partitions to wipe, so just don’t wipe the one with the factory restore files on it. 😃 ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 5, 2008, 11:35am UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/5 "2008-06-05T11:35:35Z")
If you’ve wiped, repartitioned and reformatted the drive, then there should be nothing left that ordinary data recovery programs (running on the machine itself) could retrieve. Data recovery experts could open it and possibly find something interesting by scanning the platters with specialist equipment and inferring previous states of the magnetic subdomains by scrutinising their fringes. If you’re afraid of the latter happening, then the best way to proceed is probably to remove the drive and physically destroy it (drill some holes right through it, then burn it in a bonfire), then replace it with a new one before selling the machine. If you’re just concerned about Joe Random running some undelete program and accidentally finding out about your goat porn, then repartitioning, formatting and reinstalling from scratch should be plenty good enough. ---
**Author:** ![Mijin](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mijin/32/9369_2.png) [@Mijin](https://boards.straightdope.com/u/Mijin)\ **Post date:** [June 5, 2008, 12:49pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/6 "2008-06-05T12:49:26Z")
Instead of deleting files via Windows itself, use Shredding software (this is the term to Google). I use the shredder that comes with PGP (Pretty Good Privacy). …but if you’ve already deleted the files in Windows (and emptied the recycle bin :smack: ), it’s a little late for that. You’d have to recover the files to then delete them “for real”. ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [June 5, 2008, 1:39pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/7 "2008-06-05T13:39:48Z")
[QUOTE=Mangetout] If you’ve wiped, repartitioned and reformatted the drive, then there should be nothing left that ordinary data recovery programs (running on the machine itself) could retrieve. Data recovery experts could open it and possibly find something interesting by scanning the platters with specialist equipment and inferring previous states of the magnetic subdomains by scrutinising their fringes. [/QUOTE] On the contrary. I’ve been able to recover deleted partitions and files from a formatted and overwritten hard disk using a free tool that I downloaded. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 5, 2008, 2:04pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/8 "2008-06-05T14:04:43Z")
Surely not after they’ve actually been _overwritten_? How does that work? I know it can be done by taking out the platters, but how can software tell a hard drive to read what part of it _used to contain, before it was overwritten by something else_? ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [June 5, 2008, 2:25pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/9 "2008-06-05T14:25:17Z")
[QUOTE=Mangetout] Surely not after they’ve actually been _overwritten_? How does that work? I know it can be done by taking out the platters, but how can software tell a hard drive to read what part of it _used to contain, before it was overwritten by something else_? [/QUOTE] I think it’s a case where a disk was repartioned and formatted, and some of the existing data was overwritten. You can’t do a low-level format on modern disks, and high-level format programs may actually write very little data to the disk. The ATA/ATAPI standard for hard disks has a “secure erase” feature that is supposed to address this problem. The problem is that you need an operating system or utility program that allows the user to send a “secure erase” command to the disk drive. [How to REALLY erase a hard drive](http://blogs.zdnet.com/storage/?p=129) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [June 5, 2008, 2:40pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/10 "2008-06-05T14:40:43Z")
[QUOTE=mks57] [How to REALLY erase a hard drive](http://blogs.zdnet.com/storage/?p=129) [/QUOTE] Take off and nuke the drive from orbit. It’s the only way to be sure. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [June 5, 2008, 3:34pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/11 "2008-06-05T15:34:34Z")
The OP doesn’t want to erase the HDD which makes things very difficult. Can’t you write to Sony for a set of restore CDs? ---
**Author:** ![Peter\_Morris](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/peter_morris/32/359_2.png) [@Peter\_Morris](https://boards.straightdope.com/u/Peter_Morris)\ **Post date:** [June 5, 2008, 4:30pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/12 "2008-06-05T16:30:28Z")
[QUOTE=Mangetout] Surely not after they’ve actually been _overwritten_? How does that work? I know it can be done by taking out the platters, but how can software tell a hard drive to read what part of it _used to contain, before it was overwritten by something else_? [/QUOTE] I don’t know how it worked but it did. In my computer I had 2 hard drives. Drive 0 - Windows Vista. Drive 1 - (taken from old, defunct computer) 4 partitions. 2 were Win XP (non working on my new computer) There was a data partition, where I kept all my vital documents, and a partition where I kept all my downloaded movies. Anyway, I took in my computer for repair. The shop helpfully reformatted both disks for me, and installed Vista back on Drive 1, thus overwriting it, partly at least. They were not following instructions. :rolleyes: (Note to self : backup more often, Pete.) Anyway, even though it had been formatted, I was able to run recovery software and get back the entire data partition. Bits of the other partitions were available too, not that I needed them. Some was unrecoverable, but that didn’t matter. Anyway, the moral is that formatting does \*not \*make the data unrecoverable. ---
**Author:** ![fluiddruid](https://avatars.discourse-cdn.com/v4/letter/f/c2a13f/32.png) [@fluiddruid](https://boards.straightdope.com/u/fluiddruid)\ **Post date:** [June 5, 2008, 4:44pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/13 "2008-06-05T16:44:23Z")
What you want is software that will overwrite the entire drive (such as with all zeroes). [Here is a free utility to do it.](http://www.download.com/Active-Kill-Disk-Hard-Drive-Eraser/3000-2092_4-10188745.html?tag=lst-0-1) You’ll have to re-install the OS afterward but I don’t know of a good way to keep some data but make sure other data is wholly removed from the drive. It’s worth reinstalling Windows afterward. Sorry. ---
**Author:** ![Red\_Barchetta](https://avatars.discourse-cdn.com/v4/letter/r/da6949/32.png) [@Red\_Barchetta](https://boards.straightdope.com/u/Red_Barchetta)\ **Post date:** [June 5, 2008, 5:08pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/14 "2008-06-05T17:08:29Z")
If I were to download say, a gig sized file, then copy and paste it over and over until my harddrive’s space was consumed, would that work? ---
**Author:** ![Duckster](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/duckster/32/1244_2.png) [@Duckster](https://boards.straightdope.com/u/Duckster)\ **Post date:** [June 5, 2008, 5:16pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/15 "2008-06-05T17:16:43Z")
[QUOTE=fluiddruid] What you want is software that will overwrite the entire drive (such as with all zeroes). [Here is a free utility to do it.](http://www.download.com/Active-Kill-Disk-Hard-Drive-Eraser/3000-2092_4-10188745.html?tag=lst-0-1) [/QUOTE] Go to the source web site for the most up to date information on KillDisk —\> [http://www.killdisk.com/](http://www.killdisk.com/) Also, you may want to consider destroying the partition by using [Microsoft’s delpart utility](http://www.google.com/search?q=delpart). ---
**Author:** ![NineToTheSky](https://avatars.discourse-cdn.com/v4/letter/n/b5a626/32.png) [@NineToTheSky](https://boards.straightdope.com/u/NineToTheSky)\ **Post date:** [June 5, 2008, 5:42pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/16 "2008-06-05T17:42:30Z")
[QUOTE=Red Barchetta] If I were to download say, a gig sized file, then copy and paste it over and over until my harddrive’s space was consumed, would that work? [/QUOTE] I think this all depends on how important secure deletion is to you. In ascending degrees of security, the question you need to ask yourself is, if you just delete your files, how likely is it that someone will use an undelete program to retrieve them; If you format your hard drive, how likely is it that someone will use a more sophiscated program; if you use one of the secure deletion programs (where your data can be overwritten 35 or more times)… The likelyhood is that no-one’s going to bother, but by using a secure deletion program you can be sure that your data’s gone. Your method seems like an awful lot of effort that would, at best, not be terribly secure. ---
**Author:** ![robby](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/robby/32/11048_2.png) [@robby](https://boards.straightdope.com/u/robby)\ **Post date:** [June 5, 2008, 7:00pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/17 "2008-06-05T19:00:50Z")
I’ve had very good luck with this free utility: [Eraser](http://www.heidi.ie/node/6) ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [June 5, 2008, 7:26pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/18 "2008-06-05T19:26:40Z")
[QUOTE=Red Barchetta] If I were to download say, a gig sized file, then copy and paste it over and over until my harddrive’s space was consumed, would that work? [/QUOTE] That would work nicely. For your situation, the goal is to overwrite all of the free space on the disk, ensuring that the contents of any deleted files are destroyed. Someone still may be able to recover the names and sizes of the files, but not the files themselves. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [June 5, 2008, 7:58pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/19 "2008-06-05T19:58:18Z")
Given that the OP is insistent on not deleting Windows, what about all the stuff in the registry? ---
**Author:** ![drachillix](https://avatars.discourse-cdn.com/v4/letter/d/48db29/32.png) [@drachillix](https://boards.straightdope.com/u/drachillix)\ **Post date:** [June 5, 2008, 8:32pm UTC](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857/20 "2008-06-05T20:32:07Z")
[QUOTE=GSV Consolation of Dreams] The restore files SHOULD be in a separate partition on your hard drive. I’ve used [Darik’s Boot and Nuke](http://dban.sourceforge.net/) several times before without any problems. It’s free, open source and simple to use. You can specify which partitions to wipe, so just don’t wipe the one with the factory restore files on it. 😃 [/QUOTE] A seconding for Dban, if you delete partitions without overwriting there are plenty of $99 or less data recovery programs that can pull hundreds of intact files off the drive. [Next page](https://boards.straightdope.com/t/selling-my-computer-how-do-i-completely-wipe-the-hard-drive/451857.md?page=2)