If they're commercial double layer DVDs, then you won't be able to burn all the data onto a single layer DVD-/+R/RW. There's just not enough room.
If they're single layer DVDs, and they're CSS encrypted films, then you'll have to decode them with DeCSS, then burn them onto blanks. The reason for this is that (most) blank DVDs aren't writable on the part of the disc where the keys go, so the contents of the DVD have to be descrambled before burning.
If you haven't got the copyright holders permission, then this is most probably a copyright infringement. I don't know the rules on creating backups though.
Last edited by ilikejam; 08-17-2004 at 12:43 AM.