Pyinstaller onefile does not start on some Windows 7 machines
After installing around 200 Windows updates the error is gone.
The required update is addressed by KB2999226
There's a discussion about this here working towards a build side solution rather than having to install the Windows Update: https://github.com/pyinstaller/pyinstaller/issues/1566 . As of today (9th May 2017) there's still no firm solution. There are 2 solutions that have worked for some people:
Install the Windows 10 SDK and add the ucrt DDL dirs to your system path (C:\Program Files\Windows Kits\10\Redist\ucrt or C:\Program Files (x86)\Windows Kits\10\Redist\ucrt\DLLs\x64 depending on your system) before building
Use Python 3.4 to build instead of 3.5+