Thanks for this.
As written previously, I had already clicked on 'More info'. The 'More info' told me nothing useful.
My concern was that, because Windows threw up this warning, the file I had downloaded might not be the original Mnemosyne installation file but one which, because it came from SourceForge rather than Mnemosyne, might have been changed on the way. So I ran it through Kaspersky virus check (which declared it to be clean) and Kaspersky Application Adviser (which also declared it clean and said that one user - from the Netherlands - had also given it the OK). I then told Windows Defender to let it go through and have installed the software.
Cheers
Hailo
Sent from Samsung tablet.