Tuesday, November 6, 2007

Delete for good

Reader Jeff Kahan writes: I've read that even though I empty my trash, there is the possibility of someone retrieving some of the information because it is still lurking somewhere on my hard drive. If this is true, why can't I go to that particular place, see what's there and delete it myself anytime I wish?

This is an old story but it's worth telling again for those who don't know it. Put simply: When you delete a file from your computer (and it needn't be Windows, this is common to every type of PC), that file doesn't "go away," even if you empty the Recycle Bin. Rather, to save wear and tear on your hard drive and to simplify the operation, your computer just eliminates the record of where the file began. Think of your PC as containing a giant "shopping list" of all the files on its hard drive. Delete the canned peaches off that shopping list and the store doesn't actually get rid of the peaches. It just "forgets" that they are there. The space allocated to the peaches remains there until the store needs the space for something else.

There's good and bad in this. The good is that if you accidentally delete something you have a good chance of being able to get it back. The bad: So can anyone else.

These deleted files aren't accessible via Windows, but data recovery software like File Scavenger can quickly recover most recently-deleted data from your PC as if it had never been deleted at all. If you're sure you want to delete those files for good so programs like this won't work, there's plenty of software for that too. I often recommend BCWipe, which lets you permanently wipe only the free space on your hard drive while leaving the non-deleted files intact by overwriting those deleted files with lots of random data so it can't be recovered. Other software like Kill Disk does the same thing to the entire hard drive, rather than just the blank space, leaving an entirely empty, unrecoverable disk when you're done

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