In a Microsoft Windows environment, you might use an application like Daemon Tools, Alcohol, or the MS Virtual CD Control Panel to mount an ISO image so that it appears as a CD ROM drive in Windows Explorer. This allows you to access a CD/DVD image without burning it to a disc.

In Linux, you can do this via the command line. First, make a directory to mount the ISO file into. Then, execute this command from a terminal:

$ sudo mount -t iso9660 -o loop filename.iso /path/to/your/directory

The contents of that ISO will then be in that folder.

You can unmount that disc image with this command:

$ sudo umount /path/to/your/directory

Note that some disc images are NRG files, which is Nero’s file format. You can convert those to ISO format using a command line application called nrg2iso. First install it:

$ sudo aptitude install nrg2iso

and then convert the file with this command:

$ nrg2iso input.nrg output.iso

Also, some disc images are IMG files. You can simply rename the .img extension to .iso, and then mount the ISO file.