Thank you for your post.. it's at least helped me to understand how to get an image associated with a file extension..
I've actually learned how to create a custom file extension with the fopen function.
However.. now I have a new problem. Not only do I want to be able to create a custom file extension.. but I would also like my file extension to do things.. when it is open.. Ex: When a .swf file is opened.. whatever was in that file.. is displayed on the screen. I would like to have it that when a person opens my custom file.. music starts playing (or something of the like)