django-admin' is not recognized as an internal or external command, operable program, or batch file. This error can be easily fixed by using Python's virtual environment.
Setting up this environment is recommended by Django, and it will fix this error. It will also help you to prevent clashes with Python versions in the future, so a win-win situation.
I placed two posts below that will help you to fix this error. The first post helps you through the process of setting up a Python virtual environment. After having set up Python's virtual environment, you can follow the second post. In the second post, I will go over the Django Installation and help you create your first project, and give you some useful tips.