How To Securely Erase A Hard Drive
Why Securely Erase A Hard Drive? Even if you empty the recycle bin after deleting files, they are still stored on your hard drive. When you delete a file Windows does not actually delete it – the first letter of each file name is just changed to a ‘?’ – because Windows ignores any files that start with a ‘?’ it looks as if the file has been deleted – but the file itself is still there.
With the right software all of these ‘deleted’ files can be retrieved if the space they occupy has not subsequently been overwritten by a new file – a godsend if you deleted files by accident but a security nightmare if someone disreputable has access to your drive!
Can’t I Just Format the Hard Drive or Reinstall Windows? Formatting a drive does not erase files stored on it. Reinstalling Windows might overwrite some of the old files (making them unreadable) but with the huge sizes of modern drives there is a good chance that most of the old files will not be overwritten and could still be retrieved later.
How To Securely Erase a Hard Drive
Step 1 – We will use free software called DBAN (Darik’s Boot And Nuke) – you can download the latest version here. DBAN is an ISO image file so once downloaded you need to burn it to a CD as an image – see how to burn an ISO to CD. After you have burned the CD, insert it in the computer containing the hard drive to be securely erased.
Warning: Make sure there is only 1 hard drive (the one you want to securely erase) in the computer as DBAN will erase all hard drives it finds – double check this as you will not be able to recover files after DBAN has securely erased them!
Step 2 – Boot (start) the computer from the DBAN CD. If you do not know how to do this see how to Boot from a CD. Once DBAN has loaded up you should see the following screen – press the ENTER key to start DBAN in interactive (normal) mode:
Step 3 – The main menu shown below should display your hard drive to be wiped – if there is more than 1 hard drive displayed please refer to the earlier warning, switch off the computer and take the second hard drive out of the PC before running DBAN again.
Step 4 – Press the Space key to select the hard drive for wiping – it should now say [wipe] to the left of the drive as shown below:
Note: the default Method of erasing the drive is listed as DoD Short – if you have a large drive such as 320GB or bigger, be aware that the erasing process may take up to 24 hours or more using the DoD Short method. We recommend that you change to the Quick Erase method by continuing to Step 5. However, if you’re a little paranoid or have incredibly confidential data on your hard drive then skip to Step 6.
Step 5 – To change the method to Quick Erase for a quicker finish (recommended) press the M key to display the Wipe Method menu shown below:
The default (arrowed) method is DoD Short. Use the J or Up-Arrow key on your keyboard to move up to Quick Erase then press the Space bar to select it and return to the main menu.
Step 6 – You’re at the main menu. Press the F10 key to start and the secure erasing will begin, displaying progress and time remaining as shown below:
Step 7 – When the process is complete a confirmation screen appears as shown below – remove the CD from your computer and then power off by pressing and holding down the power (on/off) button until the computer switches off.
Congratulations, you have now securely erased your hard drive :-)
Alternative Methods – Quick Erase writes once over every part of the hard drive whereas the default DoD Short method writes three times over every part. Most IT professionals, including us, believe that the Quick Erase is sufficient to erase hard drives that contain only personal data. Certainly we here at Techlogon could not retrieve any data after a Quick Erase and it is likely that only law enforcement agencies and specialist security companies could have any success at all.
But if you really want to proceed with the DoD Short method then ignore Step 5 and go straight to Step 6.