The Mac comes with free applications to play your media files. The QuickTime application plays movie files and iTunes will play your music files. However, you might find that QuickTime doesn't play every format of video that you want to watch, or that iTunes doesn't play every type of audio file, or that you simply don't like using these native Mac applications. You might prefer to use a different application to play your videos and music, such as VLC, a free media player made by VideoLAN, and set it as your default player.
Click on a movie file, such as a video with a .MOV extension on your Mac's hard drive to select it.
Click "File" and then "Get Info." The info panel for the movie file will appear on the desktop.
Click the "Open With" pull-down menu and then select "VLC" from the list.
Click the "Change All" button. Now all movie files that end in that extension will open with VLC.
Repeat this process with other movie files on your hard drive, such as ones ending in .AVI or .DIVX. You can also use this procedure to make VLC the default player for audio files such as MP3s.