Make apps stop showing as mounted partitions
If you download an app, it comes packed as disc image in most cases (a file with .dmg extension). If you open this file, this drive image is mounted as new drive. You should move the application that is on that newly mounted drive to your application folder. The image file can be unmounted and deleted. Be sure not to copy the dmg file to your application directory (you can check file extensions by selecting the file and press command+i).