All these files are created by DVD packages, you put the MPEG2 files configured to be DVD compatible and you get the DVD structure and the necessary type of files.
But you say you have the files and put them in the appropriate folders.
Does that mean you did create the folders yourself?
Note that audio ts has no visible files inside, the ifo, bup and vob files are all under video ts, and unless you use Nero Recode you should respect the original set of files, to avoid problems. Maybe you are taking one or more out and just ask Nero to burn the disc?
Sorry just guesses....