On the DVD there is a folder Video_TS in which there are 4 mpeg files. These play in Nero as the video. Elements does not recognise these files as media that can be imported into a project. Elements created these files from .avi when it produced the DVD. I need to get the files back into Elements from mpeg to .avi hence "reverse engineering" - a term that was used in the good (bad?) old days trying to convert compiled code back to source code.