Download and install Kindle-For-PC
Buy a Kindle Book
Install Calibre
Find online the programs that allow you to remove DRM from your purchased books and use them
Import the book into Calibre from "My Kindle Books" in your Documents (or whatever your flavor of Windows calls it) folder, and convert the file to .epub from .mobi
Transfer to your ereader's memory via Calibre.
Easy-peasy.