I was coming across the same issue in windows 10 but updating the environment variable following the given steps below, it tends to be working fine.
I know It is a lengthy answer for the simple environment setups, I thought it may be useful for the new window 10 users. Please follow the steps below:-
1) Open Anaconda Prompt:
2) Check Conda Installed Location.
3) Open Advanced System Settings
4) Click on Environment Variables
5) Edit Path
6) Add New Path
C:\Users\RajaRama\Anaconda3\Scripts C:\Users\RajaRama\Anaconda3 C:\Users\RajaRama\Anaconda3\Library\bin
7) Open Command Prompt and Check Versions
8) After 7th step type conda install anaconda-navigator in cmd then press y