I have an Acer 5742z with a perfectly functional keyboard, except that the Fn function key has stopped working.
The thing I have tried--
--Replaced the keyboard with a known good spare from my old 5742z.
--Uninstalled and reinstalled the Dritek/Acer Launch Manager utility
--Checked msconfig to ensure that Launch Manager is listed in startup applications. It was actually listed twice, one instance linked from the Program Files (x86) folder and one from User/AppData/Roaming/Microsoft/Windows/Start Menu/Programs/Startup Programs (or a path along those lines...)
--Tried the Windows On-Screen Keyboard and online keyboard testers. Neither register Fn key depressions.
--Check BIOS for a "Fn Enable/Disable" option. No such thing seems to be there.
So, what's left? I don't think it's the hardware, but I think somehow the key is disabled in firmware or OS? Maybe I need new keyboard drivers? Or...?