Sorry if this seems a silly question, but when you changed it in the preferences to DVD9, did you then press OK in order to save your changes?
If you prefer to copy in DVD9 and do not need all the customise and copy to mobile options then DVDFab HD Decrypter is probably the best option for you, and it is completely free. There is no DVD5 option for it to default back to.
Try totally uninstalling DVDFab using XP’s Add/Remove programs control panel, then reinstall from a freshly downloaded file [B]only[/B] from the home page.
No offence is intended by this observation, but preferences not sticking sometimes means that the installer file has been downloaded from an illegal site, and/or that the registration code was not purchased.
By the way, my advice would be not to have both the full program and the cut down freeware version installed at the same time. At least on my system, this caused all sorts of strange problems until I realised my mistake.