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Selling Your Old Computer

If you have upgraded to a newer computer and are thinking about selling your old one, there is something you should consider —

Your old hard drive likely contains sensitive information about you or your business.

When you "delete" files, even if you reformat the hard drive afterwards, the information in the files could still be recoverable.

"When you delete a file, the operating system does not destroy the file contents from the disk – it only deletes some ‘references’ on the file from some system tables. The file contents remain on the disk until another file ‘happens’ to overwrite it. Any software recovery tool can restore the data if it hasn’t been overwritten yet. Hardware recovery tools may even restore overwritten files by analyzing latent magnetic traces."

—EAST Technologies

Actions you can take to keep information secure:

Wipe your hard drive

Wiping or "scrubbing" your hard drive involves deleting all of its files and following up with a program that overwrites all the data with ones and zeros. Programs such as SecureClean, Paragon Disk Wiper, and ZDelete Disk Wiper advertise that they can write several layers of code over your data, making it unreadable.

You should consider wiping your hard drive before selling it, giving it to another person, or donating it to a charity or school.

Destroy the hard drive

Hard drives are relatively inexpensive. Think about simply destroying your old one. That way, no one will ever have access to your data.

Only 8% of hard drives sold on the secondary market have been properly sanitized.

IEEE Security & Privacy January/February 2003

Try drilling it full of holes, or taking a few whacks with a sledge hammer — in addition protecting your information, it can also be very refreshing to work off the frustration you've built up against your computer!

The following study addresses the problems inherent in discarding unsanitized disk drives. Read "Remembrance of Data Passed: A Study of Disk Sanitization Practices," by Simson L. Garfinkel and Abhi Shelat (PDF format).

As always, if you have any concerns about the security of your data, please consult your trusted computer professional.