Acer Hotkey Driver
I know some laptops are set up the wrong way round (to my mind anyway) so that pressing F8 (rather than Fn+F8) would Mute/Unmute, and if you wanted a regular F8 you had to press Fn. Does it affect all keys or is it just the F1-F12 keys at the top of the keyboard - for instance does Fn+up arrow/down arrow change the volume?
Acer Hotkey Utility

Hotkey Driver For Windows 10
Acer Hotkey Manager, free acer hotkey manager software downloads. The Acer Hotkey Driver is a kernel driver to access the launch keys found on Acer's Travelmate series and similar notebooks from other vendors.

Hotkey Driver Dell
You might find something in the BIOS settings (but care is needed as changing BIOS settings can cause all sorts of problems). Close Windows 8 using the option to Restart (rather than Shut Down) and press the key (probably F2) to get into the BIOS settings. Then look to see if there are any options about Hotkeys or similar? If you don't find it then I'd always be sure to Discard Changes on exit from the BIOS settings, just to be on the safe side.