One of the most common issues I come across as a technician has to do with improperly installed applications on customers’ machines (Skype and Firefox, I’m looking at you!). The Mac OS doesn’t explicitly guide the user how to install third party software, and as such, many are left fending for themselves, often to negative results.
When one downloads a Mac application, it’s often stored within a disk image (.dmg) which cannot be modified. This is to keep the original software intact and unmodifiable by others. Double-click on the disk image, and it will “mount” on the computer, much like any USB drive or DVD disc would.
But here’s the crucial step: Do not run the application until you have copied it to your Applications folder.
Many apps will show a window that illustrates this (see article image to the right), but you’d be amazed at how many users don’t copy it and run the app from the mounted disk image itself. Doing so can (and likely will) cause the app or your computer to do wonky things. The application may need to make changes to itself or store temporary files, and it’s being opened from a disk that cannot be modified.
If you don’t see something similar to the image pictured, just drag and drop to the Applications shortcut in the sidebar or folder in your dock. Once you’ve successfully copied the new app over, eject the disk image just as you would any other disk/disc. The new software can now be opened directly from the Applications folder.
Note: Copying the application to your desktop is ill-advised, as it cannot be accessed by other users, and may lead to issues when support is needed for your computer.