How to securely erase all of the data from your Windows based computer

Do you have an old Windows-based computer you would like to get rid of but want to make sure that all of your data is securely erased? Or maybe you would like to wipe all of the data from your hard drive and perform a clean Windows installation? Either way, you'll want to make the data is completely wiped out. Here's how to securely erase all of the data from your Windows-based computer.

Back-up all folder(s) and file(s) you want to save

This is the time to double and triple-check for any folder(s) and file(s) you may want to keep. If you plan on reinstalling Windows, make sure that you have all of the installation media available. If you need to create the recovery media stored on your computer, this is the time to do it. Once the hard drive is wiped clean, the recovery media images will be gone too.

Windows XP Backup

Windows 7 / Windows Vista Backup

Windows 8 Backup

Download and create bootable media with disk wiping software

The best way to completely wipe clean a hard drive is by booting the computer up on a CD/DVD or USB drive. This way, you can erase all of the space on the hard drive. There are several free utilities for doing this, including Darik's Boot And Nuke, CMRR - Secure Erase, and PC Disk Eraser. I recommend the Ultimate Boot CD (UBCD), which has all of these and more already built-in. Just download the image file (.ISO) and use your favorite disk burning software or Windows built-in disk burning to create the bootable media. You can even create a UBCD bootable USB drive.

Encrypt the contents of your hard drive

This step may seem unnecessary, but it makes data recovery virtually impossible on the drive you will wipe. Windows has a feature called Encrypting File System (EFS) built-in, but it's disabled by default. It allows files to be encrypted transparently with a File Encryption Key (FEK). For more on EFS, check out this Wikipedia article. So even if someone could recover the data on the drive after the wiping, it would be in deplorable condition. After that, the data would have to be unencrypted, and being in such a bad condition, would be hard, if not impossible.

1. Open File Explorer / Windows Explorer (Windows logo key + E).
2. Select the file(s) and/or folder(s) you want to encrypt.
3. Right-click on the items selected and then left-click on Properties from the context menu that appears.
4. On the General tab, left-click on Advanced.
5. Left-click the check box for Encrypt contents to secure data.
6. Left-click on OK. Be patient; encrypting the folders and files may take some time.

Insert bootable media and restart the system

When you restart your system, it should boot up on the media you created. Follow the on-screen instructions. If using the UBCD, navigate to HDD > Disk Wiping for the list of utilities. Each program will have similar data destruction settings. I always look for the latest Department of Defense standard (currently DOD 5220.22-M). If you really want to clean your hard drive, just run two or more of the disk wiping programs included on the UBCD.

If your system does not boot up on the media you just created, you may have to change the computer's boot order. Check the 'splash' screen that first appears when you start your computer. Sometimes there is an option for boot device or menu, usually an F key. If not, you will have to change it manually inside the BIOS (Basic Input Output System). The BIOS can generally be accessed by pressing the DEL or F2 key when the 'splash' screen appears. It's always recommended to check your motherboard documentation on which keys are used to access the BIOS and where in the BIOS to change the boot order.