Minor Computer Problems?

I have a G72-C55DX Notebook PC. Anyways my volume button doesn't work like on the keypad or manually. Like Bringing it up on the desktop itself. Also my screen is on full screen. Like I think I accidentally pushed a button but I can't see the top part like where you put the URL. I tried pressing f11 and all the f buttons. Can you help? Also my volume button is on f9 and f10 but the only thing it does is minimize my screen. Thanks for all the help. 50points for best answer!!