Mad Jock, thanks for those links.
Did try copying the files in the Program Files to a flash drive, uninstalling it and then running from the flash drive - didn't work as it wouldnt run at all.
Have tried the Zsoft uninstaller... didnt work, though it did identify that it was installed on a date in November despite being uninstalled and reinstalled since.. so the source of that information is my problem, I suspect.
I have also used Software Install Monitor and installed in a clean windows installation - a couple of hours spent comparing the two pairs of snapshots (registry and files) has not revealed the file or key responsible. It did change the software.log and other files in the Windows directory in C:/, so wonder if that is where the info regarding the original installation date is stored....