How to Completely Erase Your Hard Disk


Authored by Kumara Velu in Computer Software 
Published on 02-14-2009

When you format your hard disk, do you think you’re completely erasing all data from it? This question is not important if you are just going to reinstall your operating system and get on with it. What if you’re going to sell your computer or give it away? You would want to make sure all data, especially private and confidential, (credit card details/passwords) is erased.

You may not have heard of the story of two MIT students who purchased 158 used hard disk drives from different sources and were able to retrieve 5,000 credit card numbers, among other private and confidential information that were supposed to have been erased.

So, when you delete a file from a computer, it is not really removed from your system. It is only made invisible. There are programs that can help you recover the deleted files. The same goes if you format your hard disk. If you have accidentally formatted your hard disk without backing up important data, this is good news to you because of the data recovery option. But if you have information you don’t wish to be available to others, you would want an option for permanent erasure.

A more reliable option is to resort to disk wiping to ensure your data is permanently removed from the hard disk. Also called data dumping, it involves writing over your hard disk with ‘useless’ data several times to remove whatever sensitive data that may remain in there. You overwrite existing data with ones, zeros or assorted characters with the help of a disk wiping software. The software will replace the master boot record, partition table and each and every hard drive sector with the ‘useless’ data.

One such software is Secure Harddisk Eraser, a freeware that can do a good job of permanently removing data from your hard disk. It overwrites every sector of the hard disk at least thrice. There’s also an option to allow you to go up to 35 times.

The way you do it is by downloading an image file. Then by using a program like WinImage you could create a program that could be copied to your floppy disk. The developer’s website allows you to download either the 3-pass or the 35-pass version.

  • Insert the disk into the floppy drive and boot your computer.
  • By default your computer will boot from the C drive. You would have to go to BIOS and set the boot drive to floppy.
  • Wait for a minute after booting for the program to start erasing your hard disk. The 3-pass mode would require about twenty minutes per GB while the 35-pass option will take three hours.
  • When you start hearing a beep every second, you know erasure is complete.
  • The final step is trying to boot from your hard disk. Remove the floppy disk and boot the computer.
  • If it’s not possible to boot from the hard disk, then it is completely erased.

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