importing DVD movie into iMovie 4

IMovie and iDVD won't work with the MPG-2 compressed content on DVDs. You need to use something like http://www.dvdxdv.com/DVDxDV.overview.htm to convert it to DV stream video that can be used in the iApps.

BTW, I assume we are not talking about a commercial copy protected DVD.

get for 20$ the Apple mpeg2 plugin

and for free the tool Streamclip

http://danslagle.com/mac/iMovie/tips_tricks/6010.shtml

http://danslagle.com/mac/iMovie/tips_tricks/6018.shtml

you'll realize some (dramatic) loss in quality, because a video-dvd uses a very lossy compression codec (mpeg2)

I back up the DVDxDV program, I spent about $25 for it, and it was well worth it. There is no visible loss in quality importing from a DVD to i Movie....and it is easy to install and use.

Toast 7 can extract individual titles and chapters from a DVD and export into a format like DV which you can open in iMovie for editing.

Are you just wanting to copy a video DVD? If so, you don't have to convert it to use in iMovie or iDVD.

If the DVD is not copy protected, you can use Toast, Popcorn or DVDImager to create a disc image of the DVD on your computer and then use either Toast, Popcorn or Disk Utility to burn the image file to a new DVD.

If you are not trying to copy the DVD itself, please describe what you are trying to do.