How can I remove the FN-mode?

Sounds like you are using an IBM or Lenovo laptop.
To turn off the NmLk (Number Lock), press and hold the Blue Fn button on the bottom left of the keyboard, and press the NmLk key - this is usually the same key as the ScrLk.
NmLk is written in blue, so is easy to miss this when you are looking across the keyboard.
Hope this helps

Barry
May 2008