There was a request on the forums for a two-line title where the first line was smaller than the second and where the spacing was a little tighter. This would work well for a series of credits at the beginning or end of your movie.
Take a look at the video and if that is something you would like, click through to the post on Adding a Custom "Directed By" Title to Windows Movie Maker. Incidentally there are versions for either XP or Vista.