First of all what are the things you want to teach him?
Windows 7/8 or Linux does not matter. I guess the main use will be listening songs, watching movies, surfing the net, at some extent changing the wallpapers,screensavers. He is not going to tweak system settings or configuring anything. If OP wants to stick with Linux, just make a folder or shortcut in desktop to all movies songs. Tell him how to connect internet or make a script to auto connect. Then tell what is firefox, and how it works.
Gradually tell him what is email, facebook. And then make him a member of tdf
..