Nero Express Problem

Need some help. I received Nero 6 when I purchased my DVD burner last year. I have not used it for several months and needed to copy a work DVD we made of a presentation. When I loaded everything in the drives and started Nero and got the window screen to click on the COPY button to start the process, the COPY button is not highlighted and I can’t figure out what is the problem. Was the Nero 6 program I received a demo one, which had a timelife on it to expire?