To get around that, we’ll run Windows from an installation DVD or a USB drive.
You can’t format the primary drive while it’s running, for the same reason that you can’t repair a car engine while driving. Your C drive (C:) is your primary drive where the operating system (OS) is located. How to format a primary drive (C:) on Windows But it’s a little different if you’re formatting the primary drive, a secondary internal drive, or an external hard drive. Formatting a hard drive on Windows is largely the same whether you’re using Windows 10 or 7.
