Windows 8 FN key permanently activated?

If I want to make my laptop louder, of course I press the volume up button. When I want to press f10, I press fn and the volume up key. But that suddenly turned around. Say, if I want to make it louder now, I press fn and the key and if I want to press f10, I press it without fn. How can I set it back to normal?

This should be convertible in the BIOS.

With some laptops you can invert the whole thing with fn + ESC. But depends entirely on the manufacturer.

Unfortunately did not help.