Forget about DVD Decryptor (Obsolete) and download/install its successor Imgburn
In order to make successfull attempt to copy a Dual Layer Navigation DVD you will need a compatible DVD writer and DL DVD's preferrably Verbatim DVD+R DL
Also the DVD writer must either allow Booktype bitsetting manually or do so automatically when using DVD+R (DVD5 and DVD9)
Consult the list of recommended writers in this section
Explanation of Booktype and bitsetting is explained in detail on sites like www.cdfreaks.com and also on the Imgburn website and forum
There you can also find numerous topics on this subject
Having complied with the above does not automatically guarantee success. There may be copy protection mechanisms in place that prevent the use of copied dvd's and the use of copied material may also lead to either temporary or permanent damage to you equipment.
Another warning is in place to consider a very rapid deterioration or wear of the equipments laser unit when using copied material. It is always inferior to an original