You may not have set your PATH correctly to point at your Git installation.
You need to add the following paths to PATH:
And check that these paths are correct. You may have Git installed on a different drive, or under Program Files (x86). Correct the paths if necessary.
Modifying PATH on Windows 10:
In the Start Menu or taskbar search, search for "environment variable".
Select "Edit the system environment variables".
Click the "Environment Variables" button at the bottom.
Double-click the "Path" entry under "System variables".
With the "New" button in the PATH editor, add C:\Program Files\Git\bin\ and C:\Program Files\Git\cmd\ to the end of the list.
Close and re-open your console.
Modifying PATH on Windows 7:
Right-click "Computer" on the Desktop or Start Menu.
Select "Properties".
On the very far left, click the "Advanced system settings" link.
Click the "Environment Variables" button at the bottom.
Double-click the "Path" entry under "System variables".
At the end of "Variable value", insert a ; if there is not already one, and then C:\Program Files\Git\bin\;C:\Program Files\Git\cmd\. Do not put a space between ; and the entry.
Close and re-open your console.
If these instructions weren't helpful, feel free to look at some others:
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