is]http://ccm.net/forum/affich-675263-dell-laptop-fn-key-is-not-working]is this option on yours?[/url]
It seems the Fn key got disabled in Windows Mobility Center. Follow the steps below to enable Fn key in Windows Mobility Center:
1. Click "Start", type "Windows Mobility Center" and press enter.
2. In the Windows Mobility Center window, please locate "Function Key Behavior".
3. Click drop down arrow next to "Function Key Behavior" and then select "Function key"