Applications Leaving Disk Image on Desktop? I'm Confused

I feel stupid for asking this but why do some applications leave a disk image on the desktop after it is installed? you can eject it and it goes away but then reappears every time you launch the program again. I noticed this happens mainly with applications you get off the web such as Google Earth. It is very annoying because I like to keep my desktop clean. So my question is how do you avoid having this disk image appear every time Google Earth launches for example. Is it normal for some programs? or did I install it wrong?

 

That's what I did. I'm positive it's installed because I have the Google Earth Icon in my applications but the Disk Image is still on the desktop. To get rid of the Image I've tried dragging it into my applications but all that does is make a copy of it.. so I still have the one on the desktop and now one in Applications.

 

ha, that worked. It hasn't reappeared yet after I launched the program so that's a really good sign. I think I was mistaking the Install Package and calling it a "disk Image".. I guess they are pretty much the same thing, what you said to do worked so it doesn't really matter. thank you