How to Wipe a Computer Hard Drive

Step1: Back up anything you want to keep, such as photos, software product keys, etc. When the hard drive wipe is complete, there will be absolutely no way to get anything on the drive back.

Step2: Download a free data destruction program. Any of the first six programs, we recommend on that list will work great because they can be used to wipe a hard drive from outside of Windows, a necessary feature if you want to wipe the drive that Windows is installed on.

Complete whatever steps are necessary to install the software or, in the case of a bootable program like DBAN, get the ISO image on a CD or DVD disc, or a USB device like a flash drive:
– If you’re using a CD or DVD, this process usually involves burning the ISO image to a disc and then booting from the disc to run the program.
– If you’re using a flash drive or other USB drive, this process usually involves burning the ISO image to the USB device and then booting from that USB drive to
get started.
– And Finally, Wipe the hard drive according to the program’s instructions.

Credit : https://www.lifewire.com/how-to-wipe-a-hard-drive-2624527