Rip the DVD, in File Mode, with DVD Decrypter.
Create new folder, ready for Dvd2one output
Run Dvd2one, pointing it at output from DVD Decryptor as source and new folder for destination and select output size.
Choose the Title, usually the largest one.
Choose the Audio & Subtitles required.
If using Nero, make sure you have the latest version, as some earlier versions had a bug creating DVD compliant files.
Also if trying to play DVD2one output in Power DVD, make sure you Select Source/Open DVD File from Hard Disk Drive and open the VIDEO_TS.ifo file.