I am making a large quantity of home videos to distribute to friends and family. When I go to copy my dvds about 1 in 3 or 1 in 5 lock up my computer completely and I have to power down. I have been using Nero and I just don't understand why I can copy a few of them and then every once in a while my computer will freeze up. It does not freeze up at any other time except when I am burning dvds. I am using a sony external dvd burner and am running with 512mb memory. Any help would be great. Thanks.