All you will need to backup your Movie is DVD Decrypter which you already have (Just make sure you have the Latest version)and DVD Shrink (You will find a link to this in Our DVD Software section at the bottom of our Forum) then you will need a program to write the Extracted files to a DVD I suggest you use Nero !!!
With DVD decrypter just make sure you go to to top Pulldown Mode Menu and select FIle then goto Tools/Settings/File Mode/ Then make sure that the first pulldown (On Startup/Select Files/)is set at all. Then all you have to do is Close DVD Decrypter insert the DVD you want to backup and start and Start DVD Decrypter and it will rip all the files into a Folder !!!
Then just use DVD Shrink to compress the Files so that they will fit on 1 DVD and then wnen that is done just write the Files with Nero into a folder VIDEO_TS on your dvd and Hey Presto you have a copy of your Movie !!!
If you need any more help just let me Know !!!