'gulp' is not recognized as an internal or external command

I had similar issue when I installed locally initially(w/o -g). I reinstalled with -g (global) and then it worked.

npm install -g gulp

you should run gulp from folder where gulpfile.js is available.

I solved the problem by uninstalling NodeJs and gulp then re-installing both again.

To install gulp globally I executed the following command

npm install -g gulp

Go to My Computer>Properties>Advance System Settings>Environment Variables>

Under the variables of Administrator edit the PATH variable & change its value to "C:\Users\Username\AppData\Roaming\npm". Note: The username in the path will be the current Admin user's name that you have logged in with.

I had the same problem on windows 7. You must edit your path system variable manually.

Go to START -> edit the system environment variables -> Environment variables -> in system part find variables "Path" -> edit -> add new path after ";" to your file gulp.cmd directory some like ';C:\Users\YOURUSERNAME\AppData\Roaming\npm' -> click ok and close these windows -> restart your CLI -> enjoy