[HELP] No preview window

[Selur]

open a Terminal Window inside "C:/Program Files/Hybrid/64bit/Vapoursynth"

your Terminal was opened in "c:\Users\Admin"
then first enter

cd "C:/Program Files/Hybrid/64bit/Vapoursynth"

before you do the vspipe calls.
Also you need to replace

"PATH TO the test.vpy"

with the actual path to the test.vpy, in example:

"c:\Users\Admin\Desktop\test.vpy"

Cu Selur