I removed the old version of grunt first, then I installed the new grunt version, and then I got this error:
D:\\www\\grunt-test\\grunt grunt-cli: The
It says you don't have a local grunt so try:
grunt
npm install grunt
(without the -g it's a local grunt)
-g
Though not directly related, make sure you have Gruntfile.js in your current folder.
Gruntfile.js