Many thanks to davegee and Jean-Cyprien for your replies.
Dave, the link in your first message doesn't appear to work.
From reading messages in the forum, it looks like my key (currently used in version 4) is valid up to version 6.5.
Due to health reasons, I can't justify upgrading to V8, does anyone thus know if version 6.5 is still available for download please?
Kind regards and best wishes,
Chris