I’ve been asked this by a couple of folks recently; Think of them as .ZIP files – they’re file which contains many other files (although they’re not necessarily compressed like ZIP files). If you have the right application to open them it would probably make sense. (Quoting Wikipedia) In addition to the data files that are contained in the ISO image, it also contains all the filesystem metadata, including boot code, structures, and attributes. All of this information is contained in a single file. These properties make it an attractive alternative to physical media for the distribution of software that requires this additional information as it is simple to retrieve over the Internet.
With ISO files you can use WinRAR to view or even to extract files to your HD; I use Daemon Tools to mount the image file. Daemon Tools will create virtual DVD drives on your system (this is configurable by you but the default is one) – to mount files you just tell DT where the ISO file by mounting – see this Flash video for how to. Once you do this a couple of times it makes more sense of what these type of files are.
Daemon will mount all sorts of image files, such as CCD, CUE, ISO, MDS – but it doesn’t list IMG files as mountable…options are to use PowerISO to view/extract or Nero to burn to a disc. I have heard if you rename the .IMG file to .ISO or change the file filter to “all files” in Daemon Tools it will open the file and mount it like every other file type it supports.
Sometimes you’ll also find you have a BIN file – this really needs a CUE file for Windows to know what to do with it (and DT). A cue file is just a config file to tell applications how to deal with BIN files.
If you’re missing the CUE file for your BIN file and want to create one, simply open notepad and type the following
FILE “<insert the name of your BIN file here>” BINARY
TRACK 01 MODE1/2352
INDEX 01 00:00:00
Obviously put the filename in as indicated. Save this as the same name as your binary file with the .CUE extension – so if you had a file called MYCOLLECTION.BIN you’d call it MYCOLLECTION.CUE.