title: npm install failure with npm ERR
body: <p>I want to install gulp globally，so I use this command   ，</p>
  
  <pre><code>npm install gulp -g
  </code></pre>
  
  <p>then throw this error：</p>
  
  <pre><code>npm ERR! Windows_NT 10.0.10240
  npm ERR! argv "E:\\nodejs\\node.exe" "E:\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "install" "-g" "gulp"
  npm ERR! node v6.5.0
  npm ERR! npm  v3.10.3
  npm ERR! path E:\nodejs\node_global\gulp
  npm ERR! code EISDIR
  npm ERR! errno -4068
  npm ERR! syscall open
  
  npm ERR! eisdir EISDIR: illegal operation on a directory, open 'E:\nodejs\node_global\gulp'
  npm ERR! eisdir This is most likely not a problem with npm itself
  npm ERR! eisdir and is related to npm not being able to find a package.json in
  npm ERR! eisdir a package you are trying to install.
  
  npm ERR! Please include the following file with any support request:
  npm ERR!     H:\npm-debug.log
  </code></pre>
  
  <p>It seems that the error occurs because when it wants to open an director ，in fact it was an file.I checked for the node_global director and found an file named gulp.cmd and a file named gulp too.So there may be conflict between them.</p>