At the beginning, I used WMM to do my AMVs, this software is very handly but he becomes rapidly inadequate when you want to create elaborated videos. Especially for applying filters or saving in another format that WMV (you can convert it but it decreases quality)
Then I decided using others free softwares. Used in combination, they are really effective :
My interface (1152x864)
(It's in french ^^')
Of course, it's a little confused, if somebody knows a soft to allow me managing theses windows... ^^
Well, I've not still posted AMV created with this, but it's an interessant alternative.
If you have comment, questions or suggestions don't hesitate