Fn+ key is modifier (like CTRL, ALT keys),they change key code to different key code, but in case of laptops they are mostly controlled by bios interrupt handler rather than operating system which makes it next to impossible to replace it by operating system software
you could try runing this command as you laptop manufacturer could give access to those hardware functions and in mobility center you could see on/off switches:
press win +r and type : mblctr