Many people encounter issues when converting movies for playback on the iPhone 3GS. When you transfer a movie to your iPhone 3GS and click play, the phone may display a warning that it cannot play videos in that format. Clearly, you need to convert the movies to a format supported by the iPhone first. So, how do you handle the video conversion?
It’s actually quite easy to accomplish this task for your iPhone. All you need to do is download a free DVD to iPhone Converter, then install it and run it.
http://www.dvd-ripper-copy.com/guide/dvd-to-iphone-guide.html