Can't you resize the window by dragging its side or bottom right corner ? (you don't mention which OS - Mac, PC - you use nor your version of Finale).

Sorry, I'm on Windows 10 and I'm using Finale 2014.5 and no, the movie window cannot be resized by dragging the sides. I'm not sure about the bottom right corner because the window is so incredibly large that I can't see the bottom right corner.

Try redefining the preferences to force the window to display within the limits of the screen.

You can also try a higher monitor definition, so you can see the edges of the window and resize it.

(using the bottom right corner is a Mac feature, I think, so forget it)

Where within Preferences would I be able to achieve this?

On Windows, you have to locate the Finale.ini file and remove it. Relaunch Finale, the file will be recreated and the video window reset to its default size.

I think you'll find the file here :

C:\Users\Me\AppData\Roaming\MakeMusic\Finale 2014.5\

Okay, I found the file and deleted it, but the movie window is still very large. Is there something else I could try to do after deleting the .ini file?

"You can also try a higher monitor definition, so you can see the edges of the window and resize it."

And there is a popup to select a size, wouldn't that help ?

I've tried setting the window to half size before selecting a video file and it doesn't change the size. I've also tried the other two options ("normal" and "double" size) and nothing changed. It always make the window the same size.