DVD Copyright

I am looking to make backups of my collection of legimately purchased DVD’s as they are getting a bit scuffed/scratched.

Can someone please explain to me how i can copy these DVD’s as some come up with a “Cannot copy copyright DVD” error message when i try to burn using NTI CD/DVD copying SW.

Any advice on SW to use and a lamens terms answer on how to coy my DVD’s would be greatly appreciated.