Error following angularjs2 Quickstart Guide error 404 'angular' is not in the npm registry

It looks like it doesn't know what registry to point to since the package names look correct.

First try a cache clean.

npm cache clean

And if that doesn't work, specify the registry directly:

npm install <packagename> --registry http://registry.npmjs.org/

I had this same issue. Then, I realized I was using npm 1.4.3. Upgraded to 3.9.2. No problems finding the repo, now!

You need to check if your npm and node.js is up-to-date (at least npm 3.x.x and node v5.x.x, as this angular team's link suggested). If not, you need to upgrade them (I have used this post to upgrade). After this, when I run npm install, the 404 error is gone, but I still have the Darwin 15.5.0 error. Then I run:

sudo npm update -g && sudo npm install -g concurrently lite-server typescript

and uninstall the local version: npm uninstall lite-server as proposed by this link. But the Darwin error still persist. Then I remove all the node_modules folder, run "npm install" command again, and now everything is fine!