Python launcher problem

[ElChino]

If I in a cmd-shell (actually it is 4NT), do:
   c:>py -3 -V & python3 -V

I get:
   Requested Python version (3) not installed  << ! from py -3 -V
   Python 3.5.0b2   << ! from the 2nd cmd.

What nonsense is this? I DO HAVE Python3 in my %PATH.
A Registry setting gone haywire?