First Goto http://www.apple.com/trailers
and click the trailer picture or link you want to download.
Lets pretend you wanted to download "My Super Ex-Girlfriend". Now you are on the page, just click the Trailer type you want to download (small, medium, large,ipod etc.)
When the page opens, right click on the address bar and then click "Copy" menu item
Now open your "Download Trailer V.2" program and paste the link to the textbox on the left of the "GET" button, then press "GET".
NOT: Be sure you verified the "Download Location". If you want to choose the path you want to download your trailers, try pressing the "..." button on the right.
After pressing "GET" button, the list of the available trailers appears on the "Trailers In This Page" list. Just Click on the one you want to download. After you click, available format of this trailer becames visible on the left list. Just click the one you want to download.
Then download begins.
Congratulations, yor trailer is now being downloded.