An .img file is a compacted set of files or directories in a single file, which is meant to be used in an image burning program. It was created to virtualize floppy disk images, but this file format is interchangeable with the more common and typical .iso file format, which contains CDFS (CD File System) formatted information. Creating an .img file is largely the same process as creating an .iso file.
Open ImgBurn and then select the icon that says "Create Image File From Files/Folders." Select multiple folders by holding "Control" while clicking on folders. Click on "OK."
Select the destination by clicking the search icon next to the "Destination" bar. Name the image, and then from the "File Type" bar at the bottom of the search screen, select "IMG file," rather than "ISO file." Click "OK" to accept.
Click the large icon in the bottom left that looks like a folder pointing to a CD. This begins the imaging job. When it is complete, it gives you a "Done" option that finalizes the image.