How do you get Function keys to work on Mac Book Pro running Windows 7 under bootcamp?
bootcamp.exe should launch upon Login. Sometimes it doesn't or at least it doesn't stay running. You can log out and log back in or try the following, it worked for me:

Open Task Manager and see if bootcamp.exe is running. If not, open C:\Program Files\Boot Camp with Windows Explorer and launch bootcamp.exe.

Function keys will work again.