YES!! Another problem!
YES!! Thank you, thank you! I finalised the disc and it works on other DVD's and the computer programs all accept it! Another problem though - when I put in my copied DVD (again just a family movie, not pre-authored, etc)- and use Shrink combined with Nero for burning a 2nd copy. The burning happens but when I try to play it on a DVD machine, it doesn't work! I feel like I'm slowly unravelling a very large ball of wool!!
Thanks so much for your patience