Thank you for getting back to me so promptly. I returned to the forum thread and tried both the links:
On Moodle 1.5 and earlier:
(a) download http://cvs.sourceforge.net/viewcvs.py/moodle/moodle/lang/en_utf8/hotpot.php
to "lang/en/hotpot.php" on your Moodle site
(b) download the files in http://cvs.sourceforge.net/viewcvs.py/moodle/moodle/lang/en_utf8/help/hotpot/
into "lang/en/help/hotpot/" on your Moodle site
Neither link is now available. Have you any suggestions?