I think I'm beginning to understand what you are doing... let me try to explain it this way...
DVDFab 5 will take a store-bought DVD, decrypt it, and write it to your hard drive, all by itself, with no burn engine at all, but it will not burn that file to a DVD.
Imgburn, VSO, Nero, or any other burn engine you wish to try will not, by themselves, decrypt a store-bought, and write it to a HD, but they will pick up where DVDfab left off.
They will take a file decrypted by a program like DVDFab, and transfer it to a blank DVD, suitable for playing in your computer or in a stand-alone player.
End result, both DVDFab and the burner of your choice will have to work together to do the job.
For convenience sake, DVDfab provides the hooks to allow you to choose from VSO, Imgburn, and Nero, to run the burning engine that satisfies you the most with its results. Within the DVDFab program, you can specify which one you want, and at the appropriate time, DVDFab will run that burner when the decryption is complete, to finish the burning job.
Basically, once you start the DVDFab program decrypting, except for changing the disks in the drive (if your source drive is the same as your target drive), the most you have to do is sit and watch.
I apologise if I sound like I'm talking down to you... from your posts, I got the impression that you seemed to think that if DVDFab didn't work, all you had to do was install a burning engine, and that would do the job for you.
The two have to work together, each doing the job they're programmed for at the appropriate time.
I hope this helps at least a little...