software to back up copywrited dvds?

Hi, I have a few questions about backing up dvds. one is it really legal to back up a copy of your own dvds?

2. What are the or is the best backing up software?

3. I currently use xcopy. For dvd's with multiple episodes of a series (peticularly Alias) what kind of software would I use. Xcopy seems to only pick up the first episode and splits it funny with only 2gig on one disk and like 200MB on the other.

4. What is up with the dual layer thing? Can we burn dual layer dvds or is that just commercial stuff? what is it about, can i overcome it without putting a dvd on two dvds backed up?