First off, check
www.apple.com/trailers and
www.comingsoon.net/trailers to see if you can find them there. You can save quicktime trailers to your hard drive if you have quicktime Pro.
If you can't find the trailer there and want to take it off a DVD, open up windows explorer and start watching the smaller .vob files that are on the DVD using windows media player. When you find the right one, note down the name of the file (something like VTS_04_0.vob) and then get DVD decrypter. Load that up and click on the .vob file you need and then click the decrypt button. That'll dump it to your HD and strip the copy protection (if there is any on the trailers? if not you can just copy/paste right from windows explorer.
To shrink that file down, get something like
tmpgenc and convert it to an mpg or avi (divx works well) and that should do the trick.
If you can't watch .vob files you can get the
K Lite codec pack, that will allow your computer to view pretty much any movie file format there is.
