IMGtoISO is a very simple tool which does exactly what its name suggests, quickly converting IMG image files to the more commonly-supported ISO-9660 format.
The program only provides a single, very straightforward dialog, so you'll already know how to use it. Just point IMGtoISO at a valid IMG file (these may also sometimes have an IMA extension), specify the name of your ISO file, click Convert and watch as the program does its work.
We were a little surprised that IMGtoISO had to be installed to achieve this; it's so basic we expected something portable.
Still, the program only requires 3.7MB of hard drive space, not exactly a big deal. And if you don't currently have a way to convert IMG files to their ISO equivalent then this is a quick and hassle-free option.
IMGtoISO is an easy-to-use disc image conversion tool