See the following links:
- http://abdelraoof.com/blog/2014/11/11/install-nodejs-without-admin-rights/
 - http://theshravan.net/blog/how-to-use-node-and-npm-without-installation-or-admin-rights/
 
Based on that perform the following steps, if you cannot use the Windows installer provided by nodejs.org
- Download node.js from https://nodejs.org/en/download
 - Put it in a separate folder and add the folder to your „path“ environment variable. Shortcut: CMD+R and enter: 
rundll32 sysdm.cpl,EditEnvironmentVariablesOpen a new command window (CMD+R) and typenode -v. This should show the current version. - Download npm from github. https://github.com/npm/npm
 - Extract the zip folder and put it into your node.js folder
 - For convenience put the npm.cmd aside to the node.exe
 - Add the npm-folder to the path env variable (see step 3)
 - Edit the npm.cmd file and change the following line 
SET "NPM_CLI_JS=%~dp0\npm\bin\npm-cli.js"to match the path to bin\npm-cli.js. Mind: %~dp0 expands to the path where npm.cmd resides - Type 
npm -vto verify the installation - In case your behind a proxy set the npm proxy by 
npm config set proxy http://user:pwd@proxy-server:port