Download the latest version of the 'DivX Web Player'. Now, search the site for the trailer(s) you want to watch and allow them to load in their entireity (you can even watch at the same time on your PC )
When the movie has finished loading, right click on the movie and select "Save Video As...". Save the movie wherever you want. Remember you can simply rename the ".DIVX" extension to ".AVI", as it contains the same audio/visual data.