My laptop is a piece of junk. The hard drive has crashed dozens of times in the last year, the power connector is hanging loose, the battery is essentially dead, and the trackpad buttons don't work. And all that was before the hinge got broken. Thankfully I was able to use someone else's hard drive, complete with an already installed operating system (although it is Windows).
But on the new Windows 7 OS, the function key seemed to be stuck. That is, when I hit the J key without hitting any other modifying keys I get a result as if I had been also pressing the function key. I searched quite a bit for an answer but all the ones I found were dealing with people who are too stupid to realize that there is a Num Lock or a Scroll Lock - not the case in this instance.
So for days I've been typing while holding down the function key. But I noticed that sometimes the text cursor would get moved, screwing up what I was typing. Looking into that, I found that I could just totally disable the trackpad - I've been using a wireless mouse (with dongle) anyway, so the trackpad was redundant at best.
Interestingly, that also fixed the function key issue. Now I can freely type again without having to constantly hold down the function key. So if you are having trouble with the function key (and its not the obvious) you might want to look into hardware or driver conflicts.
My setup: Sony Vaio laptop with a Synaptics touchpad and an additional Logitech M310 mouse.