I’ve just come across this myself, running PsychoPy3 3.03 on Windows 10 x64.
Amazingly, all you need to do is drag the window size around and it crashes the application.
Just checked version 3.0.5, and it does not appear to have this problem. It creates the C:<user>\AppData\Roaming\psychopy3" folder structure, creates a “monitor” folder and warns you in the output console that a monitor specification does not exist so creates a temporary one for you but it does not attempt download of ffmpeg.
Additionally the following code does not work in this release:
import imageio
imageio.plugins.ffmpeg.download()
It is deprecated and the following should be used instead:
pip install imageio-ffmpeg