OK thanks for the info on your system
Since you stated it started with the latest..(v7090) download leads me to believe the installer you downloaded got corrupt during the download, when you did the clean uninstall are you sure you removed all entries in the registry that is given in the guide ? also did you also re-download a fresh(new) install package from here-> http://club.myce.com/f116/dvdfab-7-0-9-0-out-july-30-2010-a-314474/
as far as the older version not working now it could be that if you used the same installer that started this issue may have re-installed the corrupt file and a clean un-install is needed before you re-install the older version...
Are you sure you removed all entries of DVDFab in the registry ?, the guides don't include Win 2000 so there may be other entries in the registry that is not outlined in the guides so you may have to manually search.