Sometimes you want to give a computer away, or even just take it to your local recycling center. You can always use DBAN (https://dban.org/) and securely nuke the hard drive, but what if you have a good Windows 10 machine and don't want make someone have to reinstall and, in some cases, purchase a new license.

Following is almost as good as DBAN. Basically, you do a factory reset on your computer, erasing all of your data files, all of your accounts, and all of your programs. The only problem is, deleting a file does not actually delete the information on the disk itself; it just makes it inaccessible without using some third party tools. Your “free space” still has all of the information, it is just marked as “you can use this for new files.”

To actually erase all data in the free space (unused part of the hard drive), you can use the Windows built in command cipher. NOTE: this does not work 100% with SSD's (see note below).

1. Factory reset machine with wipe all programs/users
2. Allow Windows to do the reset (usually takes an hour or two)
3. Set up as per your requirements
4. reboot, then log in and shut down any processes you can
5. drop to an elevated command prompt
6. Run the command

   cipher /w:c:

   and allow it to run (HOURS!!!)

The last step will fill all empty space with 00's, then ff's, then random numbers, then exit, so basically a DoD 5220.22-M three-pass wipe (https://security.stackexchange.com/questions/117724/what-is-the-difference-between-the-different-wiping-methods-used-by-dban#139709). When done, retrieving any information off the free space on the hard disk is very difficult, if not impossible.

If you have more than the one drive, repeat cipher and change the c: to the drive letter

NOTE: if you did not do a full erase on the factory reset, there may still be some files laying around. Also, the swap file will not be touched by this.

NOTE: this will take hours on large drives

NOTE: This does not work for SSD's. For a nice article on securely erasing SSD's, see the article on Toms Hardware.