Technology in terms you understand. Sign up for the Confident Computing newsletter for weekly solutions to make your life easier. Click here and get The Ask Leo! Guide to Staying Safe on the Internet — FREE Edition as my thank you for subscribing!

Does repartitioning and reformatting a hard drive clean it?


I have assumed for years that a delete/repartition and reformat of a hard
drive will wipe it clean. I’ve done this to web viruses; recently one that put
itself into the drive system folder that couldn’t be removed by Norton or
manually. So my question is does repartitioning and reformat of a drive clean

In this excerpt from
Answercast #10
I look at reformatting and partitioning a hard drive, how
thoroughly it cleans a machine, and the effect this will have on your

Become a Patron of Ask Leo! and go ad-free!

Cleaning a hard drive

The short answer is, “It depends.”

It depends on what you are attempting to do.

  • A reformat of the drive deletes all the files; which means that any file
    that existed on the machine is no longer referenced and all of the data will
    (presumably) be overwritten by whatever you subsequently write on the disk.

  • Partitioning, repartitioning the drive, or changing the partitions (in
    other words, if you’re making the partitions smaller or larger) can make it
    less recoverable.

Reformatting may be recoverable

The problem is that formatting a hard drive may not actually erase the
contents of the sectors. It’s very much like deleting a file.

It would be possible, in many cases, to “unformat” using some utilities that
can do that; or to actually use forensic tools like
that will allow you to go in and undelete files.

In other words, the free space that you’ve just created could potentially
be analyzed and the files that used to be there recovered.

Recovering from a virus

Now, if you’re looking at this as a way to save yourself from a virus,
formatting is fine. It certainly does this “delete function” that you want.

I know of no malware that comes back from deleted files.

So, in that sense, formatting the hard drive works just great.


Partitioning adds to the mix in that (depending on which partition you are
dealing with) a repartition of the machine – into the same partitions it had
before – doesn’t really change a whole lot. It doesn’t make things more or less

Changing a partition’s size will impact the partition that follows it,
making it less likely to be recovered; but unless you’re actually moving
partitions around on the hard disk I don’t see an advantage to

If you’re really concerned, and I mean REALLY concerned, about making
absolutely sure that not only are the files deleted, but that they are also not
recoverable, then I would look into a tool such as DBan. That will not
just delete the files, but override all the free space so that the files can’t
ever be recovered.

Nothing is going to survive that.

Next – Are computers crashing everywhere because of something from Russia?

Do this

Subscribe to Confident Computing! Less frustration and more confidence, solutions, answers, and tips in your inbox every week.

I'll see you there!

1 thought on “Does repartitioning and reformatting a hard drive clean it?”

  1. I found a free diskwipe app from Big Angry Dog called HardWipe that totaly, completely wipes a drive, everyhing, using the alogarithms you pick.
    I tried it on an 80Mb SeaGate I had and it works just fine. It takes a while.


Leave a reply:

Before commenting please:

  • Read the article.
  • Comment on the article.
  • No personal information.
  • No spam.

Comments violating those rules will be removed. Comments that don't add value will be removed, including off-topic or content-free comments, or comments that look even a little bit like spam. All comments containing links and certain keywords will be moderated before publication.

I want comments to be valuable for everyone, including those who come later and take the time to read.