When I run an animation in P7, the rendering happens in a popup window, and the main window isn't even visible under the popup and the leftover pieces of a dialog box!  

This screencap shows how it looks in the middle of rendering one frame.

I don't think there's a 'render to new window' main preference,
or at least I didn't set it deliberately.

For me the main problem with 7 is that animations using the P4 renderer 
don't work at all.  Every frame is plain black, whether you go to AVI or 
separate frames.

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