Background

• 1). Almost every day we read about personal or even classified information turning up on a used computer, PDA or other device sold online. No doubt the seller thought the data was removed after erasing the hard disk drive. However, the truth is deleting information take more than dropping it into the computer's trash. To truly erase the contents of a hard drive, you must know how data is stored.
  
  
• 2). Microsoft and Apple offer a user interface to the computer hardware, substituting familiar objects (icons) for actual system operations. But just as tossing a photo of Uncle Joe in the trash does not remove Uncle Joe from our lives, deleting an file with your tax information does not remove the file from the computer.
  
  
• 3). The reason for the discrepancy is the computer maintains a table that includes the location of each file. When you delete a file, the file's location is unlinked and the space occupied can be filled with new data. However, the actual data still exists.
  
  Because of this, the operating system can recover data accidentally lost. But this recovery ability can also be used to resurrect personal data you thought were safely deleted.
  
  
• 4). The answer is to securely erase data so that private information remains safely out of the hands of others. The two options include deleting and zeroing-out your hard drive.
  
  
• 5). For Windows users, free software exists to safely erase hard disk drive data. The software Eraser 5.7 deletes files and folders using Department of Defense standards. The free software is available for DOS, XP, NT, Windows 95, 98, MT, 2000 and 2003 systems.
  
  
• 6). Mac users have built-in data-shredding features. The Mac Finder includes a "Secure Empty Trash" menu option. Mac OS X users can also pick the "Erase Free Space" button in the Disk Utility application.
  
  
• 7). Both utilities acknowledge completely erasing a hard disk drive is a two-part procedure. First, delete existing data, then fill those spaces with gibberish--known as zeroing-out a hard drive. This process literally scans a hard drive and fills each location with a zero.
  
  
• 8). While Mac users have the "Erase Free Space" feature as an option built-into the Mac OS X Disk Utility application, there are several similar applications for Windows users. A hard drive can be zeroed-out following military specifications with two free Windows-based applications.
  
  
• 9). Darick's Boot and Nuke (DBAN), recommended by Princeton University, can securely wipe a number of drive formats, including IDE, SCSCI, RAID and SAS. Northern Illinois University recommends KillDisk, a free Windows application, for students wishing to donate computers.
  
  
• 10
  
  While zeroing-out your hard drive will ensure your private data is safely erased, the protection comes at a cost: your time. KillDisk, for instance, can take up to 40 hours.