Not An Image
If you find yourself with a .img file on your hands and your not sure what it is or what to do with it, here's a quick overview.
The .img files are similar to .iso files. They come from the Apple computing world, and contain a disk image, similar to an .iso. They can be mounted as you would a .iso file and the contents accessed as a mounted file system.
In theory you can burn these files as you would any iso. Theoretically, you can rename the .img extension to .iso and use them as an .iso.
That's the theory, anyhow. In practice you may have problems burning the file, dependent on how it was configured, and the settings used when it was created.
Many DVD and CD burning software, particularly in the Windows world, can deal with .img files. Some Linux burning software can burn the .img file to disc without problems.
You can mount an .img using the mount command:
mount -o loop file.img /mnt/newmount
If the img contains video content, it can be converted using software such as Mencoder or FFMPEG.
That's about it.