My friend and fellow author Leigh Barbour has written a great article on how she made her book trailer using Power Point:
Now, when you’re satisfied with the way your trailer looks and sounds in PowerPoint slide show, most of the work is done. At this point you need to convert the .ppt format (PowerPoint) to video format.
I use a tool called PowerVideoMaker…. It has a free version that you can use or you can purchase it.