Avast antivirus gives alarm: Win32:Trojan-gen for file:

Prospect4kv349b193-090126.zip\Prospect4K-3.4.9.193-Setup.exe\$INSTDIR\Activate.exe

I use Avast, not seeing that. However, virus protect typically get false positives on protected components (like Activate.exe.) It is not virused, also that download is a year old, and there have been no reported issues. You are safe.

OK.

The strange thing is that Avast has not before complained about that file.

Avast is changing constantly, that old file hasn't. It is a false positive.