Oftentimes, files that have no ending can be treated as text files. Still, Windows 8.1 kept asking me, which program to use for such files.

The solution is to provide a default program for files without extension – and this can be easily done, even without modifying the registry directly:

1. Open a priviledges Shell:
   (Windows+Q -> cmd -> Context menu -> Run as administrator
2. Enter:

   assoc .="No Extension"

3. Enter:

   ftype "No Extension"="[Path to your favorite text editor]" "%1"

4. (Optional) Enter the following to get a nicer default icon for files without extension:

   assoc "No extension"\DefaultIcon=%SystemRoot%\system32\imageres.dll,-102

Thanks to this post at Stackoverflow for the solution.