Wiping the hard drive is a necessity to avoid any chance of having personal data retrieved after you sell or dispose of your hard drive. Knoppix is a live Linux distribution that allows you to run a Linux operating system from a CD without having to install anything on the hard drive. Knoppix can also be used to wipe a hard drive using the "shred" command. Because Knoppix is not installed on the hard drive, it can erase all of the data so it is not retrievable.
Open your internet browser and go to www.knoppix.net. Click on "Get Knoppix" on the top of the screen. Click "Mirror list on the official site" link that appears toward the bottom of the page.
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Click on one of the mirror from the "download from" list. Click on the "Accept" button on the new page to be redirected to the download page. Click on the last version of Knoppix.
Insert a black CD/DVD into your reader. Save the file on your computer. Right click on the iso file when it is done downloading and select "Burn image disc" if using Windows Vista or Windows 7. If not, open your favorite burning software, use the "Burn image" function and select the ISO file to burn the CD/DVD.
Insert the newly burned CD/DVD in the disc reader of the computer whose hard drive you want to wipe. Boot the computer and refer to your manual to press the button to enter the boot menu during the boot sequence. Select the CD/DVD reader and press "enter."
Press "Enter" when the Linux boot menu appears and let the computer boot in Knoppix. Once in Knoppix, click on the "Terminal" window on the task bar to open a terminal.
Type "sudo sfdisk –l –x" and press "enter" to display a list of the hard drives currently on your system. Write down the name of your hard drive, it should be either sdX or hdX where X is a letter.
Type "sudo shred -vfz -n 100 /dev/sdX" (substitute the name of your hard drive for "sdX") and press enter to start the wiping process.
Let the program run to completion (can be several hours) before turning the computer off using the power switch.