Fn-key not working. How do I make it work properly?

[Care2dance?]

Hello all,
This is a big day because I finally registered to this forum, which I've been reading on for approx. 6 months now. All the advice gathered here on this forum makes the ownership of a ThinkPad even more worth.

My problem is that the Fn-key only works with the (strange) F7-key. I can't get it to work with F4 or F12. Of course I've searched the forum before posting, but I've been unable to find a solution so far. Fn + F3 brings up a windows saying: "Preparing to turn off screen" which after a few seconds stops responding and must be terminated through the windows task manager. What is the reason for this?

How do I get my FN-Key to work properly?

Thanks in advance.