I'm afraid that after doing some research, I have to say that this
isn't possible. The FN key doesn't return a scancode - instead, it
modifies the scancode of the key it is pressed with, inside the
Linux on a Compaq 1711T
Information on the overall details of the running Linux on a Compaq,
however the information that is of use to you is about 1/2 way down.
Linux and BeOS on a Compaq Presario 1800T
Again, about 1/2 way down the page is a section entitled, "The damn Fn
From personal experience, I can say that laptops do include some
'fancy circuitry' into them, which enables them to do things like set
the brightness/contrast in hardware (using the Fn key), and this
bypasses the normal BIOS systems - in effect, the system never
actually sees the Fn key, so you can't remap it in XP.
I'm sorry it is not possible to re-map the Fn key, however you at
least be satisfied in knowing that a lot of other users of the Compaq
systems also dislike this button.
how the compaq FN key works
how the FN key works
compaq presario FN key scan code