Newly installed Anki not starting under WIN8

Just installed Anke Desktop in standard program directory using first the current version, then tried new beta and also the last stable version: they all do not start. No error messages. No interference from Avira anti-virus during installation as far as I can see, certainly no error message. Opening Task Manager I can see Anki running in the background only. I stopped that process and then un-installed before trying another version. All to no avail.