Since Windows 8, there has been support in the OS for mounting an ISO or IMG file to a drive letter.
$ Mount-DiskImage -ImagePath C:\MyFiles\foo.iso
Remember that you need to provide the full path to the file. The file will be mounted on the lowest available drive letter.
$ mountvol F: /d
Windows 7 and older versions of Windows do not have internal support for mounting ISO or IMG file. Use the Virtual CloneDrive tool as described here to mount and unmount.