If you want to sell a computer, definitely we need to clean the data and other files to preventing identity theft. Since several method is available do to the Erase or Wipe your Computer Hard disk fully in the market, Still this DBAN free utility is good and nice to handle it because this is completely open source self contained boot disk that securely wipes the hard disks of most computers moreover it cleans totally Microsoft Windows installation of viruses and spyware too.
DBAN will automatically and completely delete the contents of any hard disk that it can detect, which makes it an appropriate utility for bulk or emergency data destruction,and they are supports via FAQ
1) Download this utility DBAN
2) Burn (write files/data to the Disk) this file to Blank CD or DVD-R. “Do not unzip this file” burn as an ISO file format.use CD Burner XP if you have any problems with CD-R or DVD-R boot media while burning you can get help from their forum page.
3) Then Boot the computer with the Disk.
4) Use the menus to select Hard Disk Tools, then Wiping Tools, then Darik’s Boot and Nuke.Once DBAN has booted, you will be presented Prompt Blue Screen.
5) In this F2,F3,F4,ENTER and autonuke choices are appear.
6) Type autonuke, then press ENTER
7) Once wiping process finished, you will got DBAN succeeded. screen
This more like geek friendly than regular user friendly. Good luck!