When you delete a file from your hard drive, the file itself is not actually deleted. Instead, windows deleted the reference to the file from the computer’s “table of contents”. This tells the computer that the space on the hard drive taken by that file is now available and can be overwritten.

Here’s the catch: the file you *thought* you deleted, is still actually there until your computer decides to actually overwrite that space. You could potentially have data you deleted months ago still sitting on your hard drive and easily retrievable.

This of course, can be troubling in situations where you are selling your old computer or have very sensitive information you very much want to stay deleted.

There are plenty of companies out there that sell software products that will wipe out that “ghost” data so that it cannot be retrieved. Their products do work, but are not necessary. Microsoft has included in Windows a wonderful little program called Cipher.exe.

When you use this program for the purpose of wiping deleted data, it is absolutely harmless to the data that has NOT been deleted. You need not fear that it will wipe out your good data.

Cipher.exe wipe deleted data in three passes to make it unrecoverable.

What Cipher.exe does is create a text file on your hard drive and starts writing zeros to that file. It will keep on filling up that file with zeros until it fills up all of the empty space on the drive or folder that you’ve specified. As soon as it completes this, it delete’s the file that it’s just made, then creates a new file and starts filling it up with ones. It then will keep writing ones to the file until it fills the drive or folder completely (and thereby overwriting all previously deleted data).

Just as before, when the drive is full, the file is deleted. Lastly, Cipher.exe creates a third file and starts writing random numbers to the file until the drive is filled for a third time. Once the drive is full, the file is deleted and your empty drive space has been wiped. It will be nearly impossible for anyone to retrieve deleted data from your drive after this process has been completed.

The command to run follows:

The Cipher.exe command must be run in a Command (DOS) window. Open a Command window by clicking Start | Run, then type in the Run box: CMD.

cipher /w:driveletter:foldername

So, if you wanted to wipe all deleted data from your C: drive while leaving all of your other data in tact, you would type the following command:

Cipher /w:c:

If you wanted to wipe all of the deleted data in a specific folder like C:temp, the command would be:

Cipher /w:c:temp

Keep in mind that the bigger your hard drive is and the more empty space you have on it, the longer cipher will take to run. Cipher can easily run for several hours. You may consider running it at night before you leave the office or just before bed, if you’re at home so that it can run overnight.

This is what the cipher.exe command will look like while running