I read a number of posts here about difficulty in updating from Finale 25 to 25.4 or other updates on Windows 7. 

Try changing the "theme" in "Personalization". 

I had inexplicable crashes and failures but had the idea to change the Windows Theme to something else:  changed it temporarily to "Windows Classic" which does away with the "Aero" stuff (required by Cubase .. but that's another story).   After that the update worked correctly and 25.4 starts up fine.