Please see http://www.hauptwerk.com/requirements for supported operating systems with Hauptwerk.
Windows 10 is not currently supported and we have not tested Hauptwerk 4.2 with it, should you decide to try it please note we cannot offer technical support should you encounter any compatibility issues.
We would suggested sticking with Windows 8 until we offer official support for Windows 10 and when it is officially released by Microsoft which appears at this time to be near the end of July.