Hi,
I have tried this approach towards solving the installation issue. Providing you exactly the precise steps to be followed so as to install and configure you system Python and NLTK ready. I assume you guys are having a 64 bit hardware and on top of it Windows 10.
2) Make sure you check the prompt "Add Python to the Path", which is the very first wizard which comes during installation. This is will install Python and add it to the path, sparing you from the trouble of setting up the environment variable so as to add Python to the PATH.
3) Launch Windows terminal --> type python --> type "python -m pip --version", if PIP is installed ( PIP will help you to get NLTK) you'll get the version. or else i am attaching a file "get-pip.py" download the file, browse to the download folder through the Window's Terminal where this "get-pip.py" file is present, run the command "python get-pip.py". PIP, installed bingo. Run the command "python -m pip --version".
4) Go ahead and run the command python to launch the python interpreter and then "pip install nltk". NLTK installed !!. Then finally, nltk.download().