How to securely erase a hard drive on Windows

Formatting a hard drive, no matter if we use the quick or slow option, will not destroy data. It merely marks all sectors containing data as “available” so that the next save process will use them, overwriting existing data. The difference between the “quick” and “regular” format options in Windows is that quick will update the TOC, while “full” will also check each sector for errors and mark defective ones, hence the operation takes longer.

Such data can be recovered, although it is a lengthy and not always successful process. If you intend to give your old hard drives to other users and want to make sure all remnants of existing data is erased, there’s a DISKPART command that can help you called “clean all”. Here’s how to use it:

  • open an elevated command prompt (search for CMD, then right-click and choose “run as Administrator”)
  • type “diskpart”
  • type “list disk”
  • find the drive in question and select it using “select disk 2” (if your disk is in fact disk 2, more on that below)
  • type “clean all” (“clean” will be faster, but won’t overwrite data)
  • wait – this is going to take a while
  • once DISKPART says it’s finished, your disk is securely erased

DISKPART doesn’t give any updates during the process, and in my experience a 1TB drive will take about 2 hours to be fully erased. Smaller drives will take less time, larger drives will take longer. This is because DISKAPRT writes “zero bytes” into every location on every sector, and the more it has to write, the longer it will take.

You may be wondering how you can find out which disk number you need to use. Obviously we don’t want to erase the wrong one. Windows Explorer won’t help us, but Disk Management can. Search for “disk man” and you’ll see a list of all your attached hard drives with the correlation of name/drive letter/storage space and disk number. This will show you what to select in DISKPART.

That’s it! Have fun erasing hard disks and SSDs.

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