it might be a mix of two or three problems:
a) NVIDIA Optimus
I think this might be the case because, when I tell the system to open vvvv.exe with the descreet 750M grxcard, fullscreen mode does not work. When I choose the onboard HD-graphics the fullscreen mode works.
user screamer apparently has the same [issues))](https://vvvv.org/documentation/((forum:dx9-rendering-not-going-fullscreen-on-windows-8.1-with-optimus-hardware)
EDIT: actually not only the fullscreen doesn’t work as soon as the GT 750M is activated, but the renderer stays plain black, no matter what’s connected to it. This only occurs when the GT750M is on (according to the Optimus Test tool).
b) scaling problem due to high-res screen
When I use the system scaling function to make the screen usable at 3200x1800 (e.g… set to 150%) the setting for V4 gets messed up after setting a renderer to fullscreen and back. V4 is still open then, but the scaling is resetted to 100% for V4, the box “deactivate scaling on high dpi settings” is ticked and the GUI is scrambled.
c) fullscreen issues due to this registry key ‘MAXIMIZEDWINDOWEDMODE’
I didn’t manage to solve the problem by removing the key or changing it o ‘0’. After a system restore it is gone for now, but the problems didn’t resolve.