Good day roughlad.
1) B a good idea to give more detail on you PC set up....OS, Hardware, Nero version etc.
2) The disk your trying to copy is it an original or a backup copy?
3) Is this a Game your trying to copy if so, many have some form of copy protection built into them so you would need to scan the disk to find its protection....and even then it depends on your hardware and yet again the software you use to read & burn it...