You will only be able to install the OS without formatting the primary C drive. But this limits your ability to clean install the Operating System. You can also extract the contents of the ISO file and install Windows from extracted files.
The ISO file can be burned on a USB drive or a DVD drive to make the drive bootable. An ISO is a single file containing all Windows 10 installation media. The Windows 10 setup comes in the form of an ISO file. We will discuss some of the ways in detail in this article. Microsoft provides multiple ways to download and install the latest version of Windows. Microsoft makes the ISO files available so that the users can download and clean install/upgrade Windows without any issues.
Windows 10 ISO images are available for download for everyone.