Hi Dev,
Thank you for your prompt response. It is quite possibly a false alarm from Sohos, as sometimes this type of software is set to be "sensitive" to be on the safe side and hence prone to false positives. I'd prefer that to some malware/ransomware infestation, however.
I downloaded the crunched version as you noted (Thanks!) and unzipped it without issues from Sohpos or anywhere else. The game runs nicely and the visual appearance is most acceptable, I have not seen any noticeable compression artefacts. Maybe this kind of download should be the default as it is significantly smaller, and it could be worth learning how to do it.
It is likely what happened to my unzip the first time will remain a mystery, as I am not keen to repeat it.
Thanks again and keep up the good work.
Regards,