Install Octave 4.0.0 for windows (free):

1) Navigate to: https://ftp.gnu.org/gnu/octave/windows/

2) Download and install latest octave-installer.exe

3) You can permanently modify the path Octave searches by editing the file:

C:/Octave/Octave-4.0.0/share/octave/4.0.0/m/startup/octaverc

as explained here