I had some issues trying to install Node on Windows 10 and found the solution.
The error was as follows:
C:\\Users\\Stephan>npm
Error: E
go to http://nodejs.org/
and hit the button that says "Download For ..."
This'll download the .msi (or .pkg for mac) which will do all the installation and paths for you, unlike the selected answer.
You should run the installer as administrator.