Tech@Work: How to Delete Files for Good

June 1, 2002

Webster’s New Collegiate Dictionary says “delete” means “eliminate.” But in the mind of your computer, “delete” translates more as “move over.”

That’s right: Deleting files on your computer system doesn’t actually delete files from your computer system. When you delete a file, the computer removes visible references to the file, but the actual data remains completely intact. Deleting files simply marks the corresponding portions of your hard drive as free space that’s available for use; the action doesn’t remove the data. Until new data is written to the exact same space, the deleted file is easily retrievable.

This explains how undelete programs and utilities work; they search the hard drive for the deleted data and match it with the previously deleted file name.

Even overwritten data may be salvageable. Computer consultants have sophisticated tools for retrieving much or all of an old file. In fact, files aren’t actually considered beyond retrievable until the same space on the hard drive has been written and overwritten at least six times.

Although this “undeletability” may not seem that important on a day-to-day basis, there may be some very good reasons to completely remove files from your system. Consider just how much confidential client data you have on your hard drive: contact management information, scanned contracts, faxed offers.

Any records you have of clients’ Social Security numbers, bank account numbers, and credit card information could be used by the unscrupulous to embezzle money or even create false identities for criminal purposes. Data on homeowners’ work schedules could alert thieves when to break in. Of even greater concern: How can you ensure that the person you sell or donate your computer to won’t be able to retrieve all of your old files, passwords, and other sensitive data from your hard drive?

If you really want to delete files so that someone else accessing your computer isn’t able to retrieve them at a later date, there’s a way. Special software utilities enable you to actually write and rewrite data over and over again to the same area of your hard drive enough times (up to 30) to truly destroy all traces of the deleted files.

Software stores sell a variety of deletion utilities, including Symantec’s Norton Utilities ( and McAfee’s Filewipe ( In addition, PC Magazine has authored a program called Shred 2 that you can download free at the magazine’s Web site ( Using Shred 2, delete your files as you ordinarily would, which moves them to the Recycle Bin. Then run the “Shred the Recycle Bin” option to destroy those files.

If you’ve deleted files from the Recycle Bin that you want back, other widely available utilities will help you retrieve them.

Shred 2 also allows you to delete entire directories on your hard drive and to clean all of the currently unused areas of your drive. This process can be time-consuming and isn’t something you need to do frequently. But whenever you sell a computer that you’ve used, such methods are the only way to ensure that the system’s new owner can’t retrieve your previously deleted files.

Real estate is a business that asks buyers and sellers to reveal a great deal of personal information. Don’t let that highly sensitive information fall into the wrong hands simply because your computer doesn’t know the meaning of the word delete.

In addition to instructing GRI programs, Stephen Canale has spoken at hundreds of seminars in 45 states, covering subjects relating to real estate sales and technology. For more information on his products, newsletter, and seminars, visit

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