I used Windows Movie Maker to design a 49 second book trailer for my Regency short story, His Secret Desire. If you have Windows XP, you already have this program. I found the program tucked away here - c:\program files on my computer. I couldn't find it by clicking on the All Programs via the Start button. To be truthful, it took a little while to get the feel of how the program works, especially overlaying the music to the photos. But after you get used to the slide controls, it's pretty easy from there.
The music I picked out for the trailer is my favorite part of the video. SoundDogs has a great selection of royalty-free music for a reasonable price. If you're wondering about the photos, I downloaded those from Big Stock Photos. I found all this information on Sonja Foust's website. A great website for all things marketing. For instructions on how to create your own book trailer, I highly recommend reading Kevin Lucia's step-by-step article or visit Sonja's website.
For a first attempt, I'm rather proud of the trailer I created. I hope you enjoy it, too. Good luck on creating your own! It's a nice addition to one's website.