Fn key got prob

My keyboard has a prob. It is like the fn key stuck. I know many said that it can be solved by fn+f11 or numlk or scrlk, but I tried, and I don hv numlk n scrlk in my dell mini 10v.

Now for the whole row from f1 to f10, the function which I suppose to hold fn then press the key, I can just use it without fn. But it doesn't affect the home, end, pg up & pg dw on my arrow key. Now what's the prob? How to solve?