Hey,
So i cannot play fallout on fullscreen which is obviously annoying as it is unplayable. I have a 4k screen and even 1080p window is tiny. I suspect that it is due to the graphics proccesor conflicting. I have intel graphics HD 4600 and gtx 960m. If i disable the intel graphics i cannot access the nvidia control panel as it says my display is not attached to nvidia GPU, which makes no sense since i have it. The game is just black screen in fullscreen and when i click the black screen it crashes by saying fallout4.exe stopped working (when both graphics are on) if either of them are off the game works but in case of leacing gtx on i can only play in 4k which is laggy as hell. when i turn off the geforce card it is laggy in like 720p. IS there anything i can do?

Intresting remark: in safe mode my screen is acting as if the intel GPU got disbaled

Things i tried:
Update drivers (both intel and nvidia)
Uninstall geforce experience install old drivers
DDU uninstall install new drivers
In Nvidia control panel say that fallout4.exe should be take care of only by nvidia graphics card.

Have you tried switch to Windows Borderless mode?

Same problem here. When I start the game, the screen goes black and crashes after a short delay or just stays like that until I close the game with ctrl+alt+sup. I switched to window borderless mode and it worked, but the screen is too little and it's uncomfortable to play. What can I do?

Well i have but it is still a tiny borderless window on a 4K screen. It is too tiny to play on it. It might be optimus techonlogy option problem but i have no idea.

Do you also have a 4k screen? If so is it a laptop? me might have the exact same problem.

I read a lot of users with Nvidia laptops (here, steam forums and reddit are full of reports) that are not able to to launch the game in fullscreen mode, like me (reported multiple times and sent you the dxdiag thorugh the support channel). I suspect something related with Nvidia Optimus.

I hope that you are investigating the problem and preparing a fix to be released ASAP (even if it's not "perfect", you can release it as a Steam beta patch, so only the ones that want to try it can grab it), since playing in windowed mode brings a lot of problems (not able to set the resolution properly, no DSR or custom Vsync/Gsync, worse preformance, more input lag, more stuttering).

I really hope you're not getting away with the fact that, since the game can be played windowed, this issue is considered of low priority.

It's a laptop but not 4k, sadly. Still it could be the same problem.

Yeah i think it is the optimus technology too. It has to be something with it since intel and geforce GPU's seperatly work fine, it's just that both at the same time create problems, only for this game. The Nvidia support was no help whatsoever, atleast for me.

I add another thing. I tried to play in windowed mode borderless, and when I clicked in new game, it started loading and the game crashed. I received a message telling me the video controller had failed and recovered.