I used node.js to install some things via npm without any problems. Now I changed nothing on my settings (Win8; no proxy, internet is working) and I can\'t install anything
Well, actually, I want to give a comment to your question. Because I have low reputation, it means I can't give a.
If you have a trouble with npm on Windows. I would suggest you take a look the common errors of npm on wiki here. Back to your problem, please make sure you are using internet connection along with proxy or not. If you are using it, please do command npm config set proxy. I found same problem on Stackoverflow and the solution is:
use
npm config set registry http://registry.npmjs.org/so that npm requests for
httpurl instead ofhttps.and then try the same
npm installcommand.
Don't forget to clear your cache by doing npm cache clean.
Although, this way can solve the problem. You should consider about the security. This way is not the safe way because it can lead to security problem since https is not used here. I don't recommend to use this on production (thanks @ivarni for pointing this out).