Wiping a Hard Drive - How to Ensure Your Data is Gone

by Keith Park


The time has come, you have put up with that clunky old PC long enough. You finally bite the bullet and go out and buy yourself a new computer. Being the Good Samaritan that you are, you plan to donate your old PC to a local charity to be given out to those less fortunate.


While your intentions are well and good, there is something you need to consider before you hand over the old hardware.

If not erased properly, all the information and data on the old PC will be available to anyone who wants to see it. There are free and inexpensive applications that will allow anyone to access data that was supposed to be deleted.

That tax return you did last year. It's there!

Your wife's resume. Right where she left it!

A common misconception made by many is that by formatting a drive this is erasing any trace of the old data. The truth is the only way to truly erase data is to write over it. Formatting a drive only resets the allocation table to receive new entries; it doesn't do anything with the data on the drive.

There are two ways to completely wipe a hard drive. One way is physically altering the hard drive and the other is using free or inexpensive software to wipe the drive.

Physically altering the hard drive will render the drive unusable when you are done, but you can be sure that your data is gone and no one will be able to access it. This procedure is recommended when you are disposing your old equipment through electronic recyclers or bringing it to the landfill. The easiest way to do this is to drill a few holes right through the hard drive resulting in penetrating the platters where the data is stored. The drive is now physically damaged and will no longer work. An alternative would be to use a sledge hammer or some other means of destroying the drive but these seem a little excessive.

The second method is to use readily available software designed to write over the entire drive. The Department of Defense (DoD) has a standard for wiping disks, 5220.22-M. According to this specification, overwriting the drive sectors three times with specific, different characters constitutes one pass. The recommendation is seven such passes to render the data completely unrecoverable however, reading data that has been overwritten even once requires expensive equipment so this probably isn't necessary. There are free and inexpensive software solutions out there that will do a good job of wiping a PC. Check out Active@ KillDisk Free version and Active@ KillDisk Pro version (DoD 5220.22-M compatible version).

Wiping the hard drive is the recommended solution when donating your old computer to a charity or business that reuses computer equipment. Don't assume that the recycler or the charity you donated to will ensure the data is gone. A lot of these places take your PC, turn around and hand it right back out without doing much more than checking if it powers on.

Don't just be content to erase only sensitive data areas; write over the entire hard drive. Data may have been copied to the operating system swap file or other unused portions of your drive that you may not be aware of. Wiping does take time; it can take anywhere from hours to days to write over a drive depending on how big the hard drive is and how many passes you configure the software to perform.

Donating or recycling your old PC equipment is a great idea, it helps protect the environment by keeping our landfills clean. But be cautious when giving away that old PC. A few preventative steps to ensure your data is truly erased could save you a lot of headaches later on.