I need to use use my laptop with a beamer/projector but the function key (F7) does not work. I think the problem is because the laptop originally came with Vista (with evrything working) but I downgraded and installed XP.

I need a solution desperately. Can someone please help me get the drivers/software/whatever is needed to that I can use the function keys (especially the one for F7 i.e. for external monitor/beamer/projector). I have tried pressing the FN key and the F7 key but no luck.

Many many billion thanks in advance.