J4nuar never play WAW in fullscreen on PC
Change your video settings without crashing the game (borderless windowed)
Make sure your game is closed before doing that.
Go to %localappdata%\Plutonium\storage\t4\players
Open the config file with the notepad to edit it.
plutonium.cfg is for singleplayer/zombies and plutonium_mp.cfg is for multiplayer
Change these 4 dvars to be like below (you can use ctrl+f to search for them)