How to Fix Taskbar Not Hiding When Playing Games in Full Screen (Taskbar Showing)
While the taskbar is showing in fullscreen, right-click on a taskbar icon (application, network status, volume, etc.) then click back into the video, game, or web browser you’re viewing. In some cases, mostly for games, this is able to fix the problem. On Windows 7, you can also attempt to force-hide the taskbar.