For Windows using the Apple USB keyboard without Bootcamp Control Panel software i.e. you aren’t using a Mac but still want to use the APPLE SUB Keyboard. Open the Registry and search for the following Key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\KeyMagic
Find the entry
OSXFnBehavior
Change the value from 01 to 00
00 is Function Keys
01 is Media Keys
Unplug the keyboard or restart the computer to reload the new value.