You may some time when downloading a software find that the file is in iso format. The iso format is an image format and have an extension after its name .iso . Mostly when you download a game from torrents you will find this format.
To install that game or software you just have to download a software named DEMON TOOLS then install the demon tools. Now double click on the game you downloaded and you will find that an extra driver is added to your computer. Now open that driver ,you will find the file is now extracted and you can proceed as by simple method by just installing the game by double clicking on the install button.