How do I turn off full-screen videos?

I used to be able to have videos simple play in the background, but now, every time iTunes hits a video in my playlist, it goes to fullscreen, interrupting my work. How do I turn this off? In the "view" menu, video playback is grayed out. I checked "preferences" but can no longer see how to turn off full-screen. I'd hate not to be able to listen to music I bought just because it's in video format.