The file format you need if you do not want a "conversion" to occur during the burning process is a 720 x 576 3000 to 9000kb/s 48hz (or ntsc equivilent) Mpeg2. But you will still need to "author" it to DVD format. This file format is extremely rare on P2P due to its sheer size in relation to the general 320 x 240 1500kb/s AVI file most video is stored in.

To download a raw DVD file structure (IE able to burn without conversion or authoring) would be extremely dificult, because even if someone was sharing all the files from a DVD, they are generally named the same across different DVD's, and you would have no idea of exactly what files belong to which DVD, or whih ones are the ones you need.