The buttons of a notebook usually have two colors of silk screen printing. Look at the silk screen color corresponding to Fn. These keys are combined with Fn, and turning off the number key is Fn+NumLK. I don't know if you have installed the driver of ASUS notebook (ATK hotkey tool program WIN XP version). This is the driver used by Fn corresponding to the hotkey. Without it, it seems that many function keys can't be used.