Minecraft [Win10] Windowed Maximized Mouse Glitch

When I play the game windowed mode but maximized, the game doesnt lock my mouse into the game, so when I look down it exits the game and effects the task bar which causes it to @alt tab@ from the game.

For example I will be mining & looking down, and if I move my mouse too far down, BAM! It click open google chrome & takes me out of the game.

***Just realised you cant see my mouse pointer in the screen shots, but I assure you the problem is real & its making the game slightly unplayable, please beleive me ***

**Look at the bottom of the screen shots where my mouse is, it shouldnt be out of the game, & because its out of the game the menu should appear but this glitch stops that so although its out of the game, I can still look around in the game**