安装nodejs后，用npm安装任何东西都报错

不知道什么原因，安装nodejs后，用npm安装任何东西都报错：

C:\Users\Administrator>npm install express
npm ERR! Windows_NT 6.1.7601
npm ERR! argv "C:\\Program Files\\nodejs\\node.exe" "C:\\Program Files\\nodejs\\node_modules\\npm\\bin\\npm-cli.js" "install" "express"
npm ERR! node v4.4.4
npm ERR! npm  v2.15.1
npm ERR! code ENOTFOUND
npm ERR! errno ENOTFOUND
npm ERR! syscall getaddrinfo

npm ERR! network getaddrinfo ENOTFOUND xn--rvg xn--rvg:80
npm ERR! network This is most likely not a problem with npm itself
npm ERR! network and is related to network connectivity.
npm ERR! network In most cases you are behind a proxy or have bad network settings.
npm ERR! network
npm ERR! network If you are behind a proxy, please make sure that the
npm ERR! network 'proxy' config is set properly.  See: 'npm help config'

npm ERR! Please include the following file with any support request:
npm ERR!     C:\Users\Administrator\npm-debug.log

然后查npm的配置，也是一脸懵逼

C:\Users\Administrator>npm config ls
; cli configs
user-agent = "npm/2.15.1 node/v4.4.4 win32 x64"

; userconfig C:\Users\Administrator\.npmrc
disturl = "https://npm.taobao.org/dist"
proxy = "http://xn--rvg/"
registry = "http://registry.npmjs.org/"
strict-ssl = false
unsafe-perm = true

; builtin config undefined
cache = "C:\\Program Files\\nodejs\\node_global"
prefix = "C:\\Program Files\\nodejs\\node_global"

; node bin location = C:\Program Files\nodejs\node.exe
; cwd = C:\Users\Administrator
; HOME = C:\Users\Administrator
; 'npm config ls -l' to show all defaults.

根据网上的教程，换了N种镜像，问题依旧存在
然后终于在网上找到个解决办法：

解决办法：

1、执行：

npm config get proxy
npm config get https-proxy

如果返回值不为null，继续执行：
（这一步很重要，一定要保证两个命令的返回值都为null,话说回来，应该出现这个错误这两个返回值有不为null的）

npm config set proxy null
npm config set https-proxy null

2、执行：

npm config set registry http://registry.cnpmjs.org/

然后你就可以愉快的安装cnpm了

npm install -g cnpm --registry=https://registry.npm.taobao.org 

然后你就可以更加愉快的用cnpm安任何东西了