r u saying that u want the people in the video to have a different head and have them in different places aswell? If it is so, then movie maker and cheap stuffs wont do it.
You need the video shot in a green screen, then you need to digitze the video and then, you need sony vegas or final cut pro or adobe after effects. and then you need to key out its colour. It isnt easy for people who doesnt know much abt softwares.