Correctly using disk images on your computer is something everyone needs to do. Most folks just double click on the .dmg and never drag the program from the image to their hard drive. So everytime they launch their program from the Dock if the image full is not mounted it mounts and then launches the application. At a client site the other day I ran into 25 mounted disk images on the desktop. So if you click on that .dmg and it mounts a disk image on your desktop. (Note a disk image looks like a flash drive and can sometimes be colored.) After you install the program or drag to program to your Applications folder, please eject it by dragging it to the trash. If it disappears from the desktop you have succeeded in dismounting it.