mounting ISO files

Is there a way to mount an ISO file, by renaming it or something? Sorry if this is a dumb question, but I am looking to download an application that is rather large, and I already have the app, but as an ISO.

What?

Macs can mount disk images without the use of any applications. It's built into the Operating System.

I agree, you can double click on the file, and the installer opens. HOWEVER, I already have said program installed (from someone else's disc), and just want to play the game, not install it. On this note, when i tried to re-install from the .iso file, and used the other persons code, it wouldn't allow me. what's the problem here?

One possibility - If the game is a copy protected game, you'll run into problems as making an ISO of a given game usually ignores the copy protection areas that verifies that the game is authentic.

a ha! (btw, the game is Sims3). so, how do i get around that?

purchase your own copy of it

discussion of illegal activities (as defined by U.S. law) is not allowed here

You should be able to mount ISO and DMG files just by double-clicking them (unless some other program has associated itself with those filetypes).