• Usually when a file is deleted, the data stays on the drive until another file overwrites it.hard drive image by iMAGINE from Fotolia.com
  
  When you delete a file from your computer, such as a text document or a picture, it may not actually be erased from your hard drive. Most operating systems take a shortcut when deleting files; instead of erasing the data, they just mark that area as empty. Since the data is still there on the hard drive it's sometimes possible to recover it, which can be a major security concern if other people have access to the computer. To erase data completely, there are a few free utilities available.
  
  

Disk Wipe

• Disk Wipe is a free publicly licensed disk erasing utility for Windows. Disk Wipe can be used from a USB stick without any installation allowing for easy usage if you have to wipe drives often, and includes several different disk erasure algorithms.
  
  

Eraser

• Eraser is another free publicly licensed disk erasing utility for Windows. Unlike Disk Wipe, Eraser is used more for cleanly erasing individual files or folder instead of entire drives. Eraser has a built in scheduling system allowing users to choose when to run the data wipe.
  
  

Kill Disk

• Kill Disk allows you to create a "boot disk," which can then be used to boot a computer directly into the disk cleaning software. Although this can be useful for some users, it is a little more complicated than other disk wiping tools. There is also a retail version of Kill Disk which includes 17 different disk erasure algorithms.