Fn key on laptop locked on

I am working on a laptop that has the Fn key stuck on. When the user uses the j,k,l,u,i,o,p keys, the letters that come up are the ones that come up as if you are pressing the Fn(function)key. How do I trun this off? How did this get turned on so I can tell him not to do it again? The computer is a Dell Inspiron 2600 Running Win XP Pro. Thanks