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Add npm path "C:\Users\{Your Name}\AppData\Roaming\npm"
to "Edit Environment variables" > "System Variables" > "Path" > "New Line"
Note: Remember, Its a hidden path on your PC. I Recommend you to enter your user_name in given path and copy paste it on file explorer to view the contents
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Windows Search - Edit Environment Variables
Click - Environment Variables
Under user variables select PATH
Click in New
Paste - %AppData%\npm
Save.
Open a terminal and check out
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Just adding a little info to the previous answers, If you have windows 7 or above then go to start and search Node.js command prompt and you will be directly shown the app. Click on it, and start working by using that command prompt for angular.