An .iso doesn't work. It is a file. It just "is." Double-clicking on an .iso creates a mounted volume on your Desktop. If that mounted volume contains one or more applications, then you should copy them to your hard drive before running them. A potential problem with .iso images as mounted volumes is that they are writable.
Long story short, you need to clarify what you are doing. If we know what you are doing, then we can diagnose your problem and give you the help that you want.