Just select the .img file as the source for the burn. An .img file may be an image of a CD in a proprietary format - not sure whether it is Roxio's or Nero's - an .ISO file is the universal format for optical disk images. When you burn it, it may create a whole CD or DVD that is an exact copy of the original.
. Just remembered, an .img file could also be a floppy disk image used to make a self-booting CD/DVD. What size is the .img file?
.bh.