This will forcibly disable VSync in the game.' Make a backup copy of this file first, then open it with a text editor like Windows Notepad, and alter the iPresentInterval=1 variable to iPresentInterval=0 and save the change. 'You can force VSync off in Fallout: New Vegas by editing a command variable found in the Fallout_default.ini file in the \Program Files (x86)\Steam\steamapps\common\fallout new vegas directory.