Write an article based on this "Back up important data. Go to http://killdisk.com/killdisk-freeware.htm in a browser. Click Download for Windows or Download for MacOS. Install KillDisk. Connect your external hard drive to your computer. Open KillDisk. Click the drive you want to erase. Click Erase Disk. Click Start. Type the keyphrase and click Ok."
If there is data on the drive you need to keep, make sure to save it on another hard drive.  You can transfer files to your computer's internal hard drive, use a USB flash drive, or upload to a cloud storage service such as Google Drive, DropBox, OneDrive, or iCloud. This is the website for Killdisk, a free disk-cleaning app that works on Windows and Mac, as well as both mechanical and solid-state drives.  Disk cleaning programs like KillDisk provide extra security by overwriting the old data with random data that prevents the old from being accessed with data forensics tools. Some other popular data-cleaning tools are DBAN Drive Cleanser by Acronis, and CBL Data Shredder. Click the download button that corresponds to the operating system you are using. By default, your downloaded files can be found in your Downloads folder on both PC and Mac.  Double-click the ".exe" file for Killdisk on Windows, or the ".dmg" file for Killdisk on Mac, and then follow the on-screen instructions to install. Most external hard drives can be connected to your computer using a USB or firewire cable. In some cases, an external hard drive may need to be plugged in using an AC adapter. KillDisk has an icon that resembles a red disk with a while "@" sign on the front.  Double-click this Killdisk icon in the Windows Start menu or the Applications folder on Mac. All disks connected to your computer are listed on the main menu for KillDisk. The drive you select will highlight in orange. Be careful not to select a disk drive you need, such as your Windows installation drive. It's at the top of the KillDisk app.  It has an icon that resembles a hard drive with a red triangle. It's in the lower-left corner of the pop-up window. If you have the registered version of KillDisk, you can select more accurate erasure methods using the drop-down menu next to "Erase Method".  You can also check "Verify erasure of [disk percentage] of each disk." The keyphrase is above the field where you enter the keyphrase.  Enter it exactly as displayed in the window and click Ok.  This begins the process of erasing your disk.  Since this method overwrites your old data with random data, it will take considerably longer than other methods of formatting your drive.