[SallySimpson]

I would try to "get ready" the DVD files with Shrink first, it will analyze the stuff to see if it's ok and will do like an exact copy of the suff ready to be burnt properly and with no errors with Nero. But be sure you have space enough in your comp, if you're gonna make an exact copy of the files and the stuff is 4 gigs sized (an example), you need 4 free Gigs in your HD.
I always do a copy with Shrink, as it "cleans" some Region Code or something the stuff might have. I got a DVD from Dime once and, after burning it, couldn't see it with my DVD Home player cos it was encoded for region II or whatever (USA and Canada, I think), so I had to clean that shit with Shrink.
But one DVD spoiled...

You can d/l Shrink for free. Info here:

http://www.dvdshrink.org/what.html