You need to be more specific. Thier are a lot of types of burning that you can do with dvd. Keep in mind that if you are trying to copy a movie etc., a backup copy of a movie you own is ok but piracy is not. If you downloaded off of p2p or torrents, if it is some freeware movie, not something copyrighted (if not you cannot discuss it here).
So to go further, what are you trying to burn to the disk, data, a movie for backup, home movies, and how did you try to do it with nero?
What are you trying to do?