Although you were offered a good solution by others I think it is helpful to point out what is really happening. As per the Anaconda 4.4 changelog, https://docs.anaconda.com/anaconda/reference/release-notes/#what-s-new-in-anaconda-4-4:
On Windows, the PATH environment variable is no longer changed by default, as this can cause trouble with other software. The recommended approach is to instead use Anaconda Navigator or the Anaconda Command Prompt (located in the Start Menu under “Anaconda”) when you wish to use Anaconda software.
(Note: recent Win 10 does not assume you have privileges to install or update. If the command fails, right-click on the Anaconda Command Prompt, choose “More”, chose “Run as administrator”)
This is a change from previous installations. It is suggested to use Navigator or the Anaconda Prompt although you can always add it to your PATH as well. During the install the box to add Anaconda to the PATH is now unchecked but you can select it.