On Windows, you can temporarily disable the Function key by pressing Fn and the designated Fn Lock key at the same time. To permanently disable Fn in Windows, turn it off in BIOS. Why Disable Function Keys? Some common reasons to disable function keys include: Prevent. This section will walk you through the steps to disable the Fn lock on your Windows 11 machine. Pressing the Windows key + I is the fastest. To do this, hold the Fn key and press the Esc key.