C# .NET - How to protect my video files from copy on pendrive

Hello friends
I 'm working on a project that is a series of training videos
its a program that catogories kessons and when users clicks on the lesson subjects it playes related video
all of this works are easy but i want to write this videos on pendrive and i want to protect videos and pendrive application by licensing
and I should protect my videos from being copy !
how can i first encrypt my videos on a file and then play them in my program , in this way i think no one then can copy my video files, any idea ?
how can i do this works ?

give some codefiles and links its very urgent..