What video editing programs do you have?
What format do you want to end up with? (quicktime, realvideo, whatever)
If you authored the DVD yourself this should be painfully easy, it almost hurts to try to explain it.
Open the file that you used when you burned your DVD with whatever editing program you used on the footage from your camera.
Find the segment of video that you want you want. Depending on how your program works you may need to assign start/end points or you might just have to highlight the segment you want to work with.
Cut or copy it out of the video as a whole, do whatever you need to to get that 4 minute segment isolated from the rest so you can work on it alone.
save it.
If I were you I would get
Total Video Converter which is rather easy to use and work from there.
[Link]