Function key locked?

Hello,

I am using an Asus machine and for some reason the fn key is locked on - When I press f6 for instance, instead of changing the brightness as I'd like it performs the f6 function. I don't want it on!! I have tried to press fn and num lock but that has not yielded any results. I have also searched my onscreen keyboard in order to see if there is something there I could change but have not yielded success there either. Advice? Thank you!