Copy DVD?

[jc]

I have a new G4 with the SuperDrive (DVD-R/CD-RW) and a home movie on 
DVD that I would like to duplicate (home movies from 1936 put onto 
Video tape and from there to a DVD disk by a commercial company). I 
copied the contents of the DVD to my hard drive and then dragged them 
to a new DVD-R disk. Took about 20 some minutes to copy but when I 
tried to play it there was nothing. Looked at the disk again and it 
says that it's empty.

Am I doing something wrong or is what I want to do not possible with 
my computer? I don't need to format the disk first do I?

Help!
-- 

-jc