On most Mac apps, clicking the green button in the upper-left-hand corner of a window resizes that window to fill the screen. But for historical reaons, in iTunes, the behaviour is different. Clicking on the green button toggles to a mini-iTunes controller window.
This tip is that holding down the Option key will restore the normal behaviour to iTunes. e.g. Option-clicking the green button will make iTunes resize its window appropriately to the screen that it is running on.
Tip source:
Solve iTunes window size issues when removing displays (http://www.macosxhints.com/article.php?story=20091231072047135)
Posted Jan 7, 2010 on www.macosxhints.com (http://www.macosxhints.com/)