How to Format a Computer Via DOS

By Editorial Team

Updated July 21, 2017

Formatting--or reformatting--a computer's hard drive can be necessary if you're setting up a new PC, reviving a corrupt hard disk or installing a new operating system. The process is fairly simple, but there are a few things you should know before you begin.

Make sure you have a bootable floppy disk or CD.

Insert the disk into the computer, and turn it on. The computer will boot to a black screen showing only an "A:>" prompt or a prompt indicating the letter of the drive you booted from. You can also accomplish this by rebooting your computer with the disk in the drive.

Type "format c: /s" and hit "Enter." The formatting process will begin.

Hit "Y" on the keyboard for "Yes" when asked "Are you sure you want to erase everything on drive c:," and then press "Enter."

Remove the disk, and reboot your computer. It will boot to the "C:>" prompt from the hard disk.


DOS is a generic acronym for "Disk Operating System" and can be associated with several operating systems, including Windows, Linux and Macintosh. On older systems, it can also be MS-DOS. Make sure you're formatting your hard drive with the DOS specified for the operating system you plan on installing.

If you don't have a bootable floppy disk or CD, create it by inserting a blank disk into your computer and typing "format a: /s" from the C:// prompt on your computer before beginning the process. "A:" can be replaced by the letter for whatever drive you are using to begin the reformatting process.