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kolax

macrumors G3
Original poster
This is really irritating me.

I changed all mp4 files to open with QuickTime. Yet, if the mp4 file isn't in my iTunes Library, it will get copied to my iTunes Library, otherwise it will open QuickTime.

What the...?!
 
Under->Preferences->Advanced

Do you have "Use iTunes as the default player for Audio files" checked? This could be your problem.
 
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