Debian based distros:
sudo apt-get install python3-tk
RPM based distros:
sudo yum install python3-tkinter
For Windows, I think the problem is you didn’t install complete Python package. Since Tkinter should be shipped with Python out of box. See: http://www.tkdocs.com/tutorial/install.html . Good python distributions for Windows can be found by the companies Anaconda or ActiveState.
Test the python module
python -c "import tkinter"
p.s. I suggest installing ipython, which provides powerful shell and necessary packages as well.