How To Prevent F4 From Closing Window

F4.I really disliked the fact that a slip of the hand that results in me pressing F4 means closing a window, so I went to BIOS mode and added the prefix of 'Fn +.' So I pressed F4 to try it out and it performed the exact same function. So naturally I tried pressing Fn + F4 and it did the same thing. I'm pretty irked that F4 = Fn + F4.

So the question of the day is: how do I prevent F4 from closing my window? I don't want to disable it completely because I want to attach another hotkey to it (ex: F4 = go back one song for a music player.) If I wanted to do that, I would've used Sharpkeys.