Here's food for thought from Jim Hamm, "In this newsletter from Small Dog Electronics is an article on installing applications on a Mac. In the article it states once the disc image is opened on your desktop it should be dragged to the applications folder on your Mac. Then the application should be opened and installed within the applications folder -- not on your desktop.
"I haven't been doing this. I usually just open the app on the desktop and install from there. After reading this article I plan to change my ways...." Jim