Ok dont buy an DVD recording software, if your Nero wont copy it then its unlikely additonal software will do any better. If its in DVD movie format then DVD shrink should work ok.

I would try a straight copy using nero though as if the dvd is not copy protected then dvd shrink is not needed. Make sure your nero is set to copy to the HD first (not on the fly) and try the lowest recording speed.

Alcohol 120 and Clone Dvd are good programs and both offer free trials.