How can I make a video with half of the screen different from the other
You have to have a good program inorder to do that. Not something like Windows Movie Maker... You need something ALOT more high tech than that.
do you need Windows live movie and you have to have at least a Windows 7
If you have an apple (and I presume Android) portable device, there is an app called "Game Your Video" that can easily create split videos! :)