This article has been described on the basis of Windows 8, 8.1
Windows SmartScreen which was introduced since Windows 7, protects non-signed app from starting.
All of the installation files of Windows apps from Digutsoft hasn't signed, so SmartScreen filter blocks our installation file to start. (But after install, program runes well.)
In this case, click 'More info' text, and click 'Run Anyway' button. Then installation file will run.