For full Story: someone has the exact same problem here: https://forum.qt.io/topic/50118/windows-qt-deployment-not-working-vs2010-qt-5-4-0
Short story and Question:
Is there anything Qt-Installer sets during the installation process of the SDK? My Application works only on machines where Qt is installed (C:/Program Files/Qt). I checked the env variables but there is nothing Qt related.
Any help appreciated.