Wiping a Hard Drive

Archived Q&A and Reviews

  • See also: Computer Support & Repair
    August 2009

    Hi, Need advice on how to completely clean my computer before re-selling. Thanks everyone. concerned about privacy & security

    You cannot completely wipe your hard drive clean - you just can't do it. Even if you delete everything it still leaves a trace of your old stuff. Something can always be recovered from it, and you can't tell what it will be - your tax returns or some random photos. If you're really concerned about your data, then take out the hard drive and smash it with a hammer. Seriously. It's the only way to guarantee that nothing can be read from it. Then sell your computer without a hard drive (they cost maybe $100-150 to replace).

    Your other, less secure option is to delete everything and then do a clean install of your operating system. Assuming you use Windows, your computer probably came with disks with the OS on them. If your computer is already 2nd or 3rd hand and you don't have the license info then buy a Windows upgrade product and do a clean install. Only the pros with sophisticated technology would be able to pull any of your old data off the computer at that point.

    I think people get too paranoid about other people getting data from their old computers. It takes a very sophisticated user and software to pull up deleted files, and even then the recovered images are often incomplete and fragmented. I'd worry more about non-shredded credit card receipts in your recycling. That said, there are programs out there that can scrub your disk by overwriting the space where deleted files ''live'' multiple times. The Department of Defense standard is three passes. Pareto Logic Privacy Controls (just one example; Google will lead to many, and there are free ones as well) lets you go up to seven passes. The same functionality is in the McAfee security system that comes with an AT DSL account, and it allows for up to 10 passes.

    Create a junk folder on your hard drive. Find a large file of any sort, put it there, and proceed to make multiple copies of it. Actually, just copy the entire contents of the folder each time, so you'll go from 1 file to 2 to 4 to 8 to .... (the old kernel of corn on the chessboard story). Yes, it takes some time, but not all that long depending on the size of your hard drive. You want to fill your entire drive, manually overwriting all the sectors where deleted files reside until the space is needed, so you're telling the computer to use that space. You can use the Windows Defragmenter (which I hope you've been using all along) to check the available space on your computer. You can take it all the way to 0% (although that's probably overkill). Then, delete that junk folder with one of the above programs that shreds and overwrites the same files you just used to overwrite whatever had been there before. I dare anyone to find anything useful on your computer after that.

    Or, as previous poster indicated, you can reformat -- if you have all your installation CDs. Plus, if you go that way, you could actually decide what programs to reinstall. Not Snoop Dog

    March 2003

    I would like to give away/recycle my old CPU - but I am very concerned about sensitive personal/financial information still retrievable on the hard drive (despite having ''deleted'' all files). With all the horror stories about identity theft and ripoff of financial info from old computers, does anyone know how to wipe hard drives completely clean? (Sounds like this could be a great small business venture for some enterprising techie!) A cautious recycler

    I'm forwarding an e-mail I received. Basically, it's a link to useful info:

    Two MIT graduate students say they found personal and corporate information on used disk drives bought off the Internet and at swap meets.

    Old hard drives yield data bonanza By Sandeep Junnarkar Staff Writer, CNET News.com January 15, 2003, 12:35 PM PT http://news.com.com/2100-1040-980824.html Signed: Cautious too.

    If someone really, really wants to read your hard drive, there is almost no way to prevent them, but it's generally not worth their time. When you think about the many places that have access to your social security number and credit card numbers and how much you're trusting to their good sense and privacy policies, worrying about someone reading an old hard drive from which you have deleted documents is far down on my list. That said, the easiest thing to do is to reformat your hard drive (don't do this until you're sure you've saved all documents you want) and reinstall the operating system. Or, don't even bother reinstalling the operating system if you want to leave up to the new owner. Instructions for reformatting the hard drive are in your Microsoft pamphlet (I'm betting you have Windows of one sort or another).
    Wiped My Old One Clean
    Your answer is here: http://www.bcentral.com/articles/komando/126.asp

    Option 2 (reformatting the hard drive) is probably what you want. Norm

    Formatting/partitioning hard drives do not erase the information on hard drives. That and ''deleting'' files only removes information about how to locate the file on your drive, but not its contents. The solution for unrecoverable erasure is to ''wipe'' the file or drive. It's a repetitive process of overwriting all 1's, then all 0's over the file contents. Four or five times of that will sufficiently hide any original data.

    The Pretty Good Privacy (PGP) is free software mainly used for encrypting emails and files, but it includes a file and freespace wiping function.

    Just be forewarned that it's forbidden to export the software out of the U.S.. kim