The Key File is a small encrypted file containing the user’s registration details. When present in the installation directory, it unlocks the software, removing the startup nag screen (the "nag screen" requires the user to click a specific button like 1, 2, or 3) and enabling full functionality.
: Once you own a key, it remains valid for all future versions of Total Commander until further notice. Total Commander Key File
In some legacy versions, the key could be embedded into the registry. This is no longer standard practice. Stick to the flat file. The Key File is a small encrypted file