You need to run the cmd prompt from the Scripts directory of Anaconda where ever you have the Anaconda parent folder installed. I happen to have in the root directory of the C drive on my Windows machine. If you are not familiar there are two ways to do that:
A) Use the key combination Win-key + R
then type cmd
and hit return to launch the terminal window and then type: cd C:\Anaconda\Scripts
(or whatever directory path yours is).
B) Navigate using windows explorer to that Scripts directory then type cmd
in the address bar of that window and hit return (that will launch the terminal already set to that directory).
Next type the follow commands waiting in between for each to complete:
activate root
conda update -n root conda
conda update --all
When complete type the following and Navigator hopefully should launch:
anaconda-navigator