I have make back up some of my software collection in a DVD-R using Nero 8. I added more files to that multisession disc later. I have used writing speed for the first occasion 20x and then 16x. The DVD is now become unreadable in my system - Platform: Vista Ultimate sp1. The file system in the disk is showing UDF. Is there any possibility of recover the data from that dvd? If yes, how?