How to open .iso file?

Guys i really have this problem that kick my butt off!
I'm a government employer and i work as draftsman. My skill is to build construction site plan thru CAD. I am trying to install Autocad 2008 in my laptop but apparently, the file format of the setup is CAD.iso which is it cannot open the setup?
How does this file works? Do i have to install again the installer? As i remember this cd was work on my friends personal computer. So it has to be work on my laptop too.
I have project to do and shall be finish next week. A little help please thanks
