Many popular software packages are available for download in the form of a CD or DVD “ISO” Image file. These files usually end in the extension *.iso and are designed to burn to an optical disk with ISO Image Burning programs such as Roxio.
If you want to extract files and folders from the ISO image without burning a disk, you’re in luck. The open source 7-Zip program is capable of opening and extracting the contents of an ISO file as if it were a standard Zip archive. You can download the Windows GUI for 7-Zip at http://www.7-zip.org/ .
Linux users can “mount” an ISO file from the command line to view and extract files, google for “linux mount iso” for examples.
UPDATE: A lesser known feature built into Windows 8 and Server 2012 – the native ability to mount ISO files (accessible via local drive letter). See the following article for more details: Mounting .ISO files Directly is Awesome Feature in Windows 8 [& 2012].