After installing the Linux subsystem for Windows, open bash and run the following commands.

curl -sL https://deb.nodesource.com/setup_6.x | sudo -E bash -
sudo apt-get install -y nodejs

After that, both node and npm will be available from bash.

To uninstall NodeJS and NPM run this:

sudo apt-get remove nodejs

See also: https://nodejs.org/en/download/package-manager/