As well as an .avi file (approx 700Mb) I have files with the extensions .sub, .nfo, .idx and .md5. What are these files ? I'm hoping that the .idx file is an "index" file which indicates where the chapters should be, and the ".sub" file is a "subtitles" file - but I don't know how to pull this all together and write the DVD with indexing and subtitles etc all integrated. I'm using Nero. Someone please help !