Set QuickTime X for Snow Leopard to automatically start playing videos when you open them:
1. Open the Terminal application in the Utilities folder.
2. Type: defaults write com.apple.QuickTimePlayerX MGPlayMovieOnOpen 1
and press Enter.
That’s all. Now the movies will open automatically. If you wish to undo this, use this command:
defaults write com.apple.QuickTimePlayerX MGPlayMovieOnOpen 0
