I have a few friends that waste a lot of time copying DVD. The reason a lot of people have failures in making a successful burn is that they do not know if thier DVD player is DVD+ format or DVD- format. The new DVD players have multitude of formats they can read. But if your DVD player is slightly aged it may only read one format.
And there lies the problem. You maybe burning DVD+ for example but your DVD player can only read DVD- .