Ionic Installation Error

Hello experts, I have been struggling for hours to install ionic on my windows machine, each time I try I get the error below

C:>npm install ionic -g

node-sass@3.4.2 install C:\node_modules\ionic\node_modules\node-sass
node scripts/install.js

Binary downloaded and installed at C:\node_modules\ionic\node_modules\node-sass\vendor\win32-x64-46\binding.node

node-sass@3.4.2 postinstall C:\node_modules\ionic\node_modules\node-sass
node scripts/build.js

C:\node_modules\ionic\node_modules\node-sass\vendor\win32-x64-46\binding.node exists.
testing binary.
Binary is fine; exiting.

spawn-sync@1.0.15 postinstall C:\node_modules\ionic\node_modules\spawn-sync
node postinstall

npm ERR! Windows_NT 10.0.10586
npm ERR! argv “C:\Program Files\nodejs\node.exe” “C:\Program Files\nodejs\node_modules\npm\bin\npm-cli.js” “install” “ionic” “-g”
npm ERR! node v4.4.3
npm ERR! npm v2.15.1
npm ERR! path C:\ionic.cmd
npm ERR! code EPERM
npm ERR! errno -4048
npm ERR! syscall open

npm ERR! Error: EPERM: operation not permitted, open ‘C:\ionic.cmd’
npm ERR! at Error (native)
npm ERR! { [Error: EPERM: operation not permitted, open ‘C:\ionic.cmd’]
npm ERR! errno: -4048,
npm ERR! code: ‘EPERM’,
npm ERR! syscall: ‘open’,
npm ERR! path: ‘C:\ionic.cmd’ }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.

Please help