That was outstanding detective work! MAHALO!
I have Opera installed on Vista now, all preferences set and I am using it to type this. It imported the Fx bookmarks again so I did what you suggested and deleted the bookmarks.adr file. It recreated a new bookmarks file but withOUT the Fx bookmarks.
I then went into Opera:config and checked the preference to disable importing bookmarks so it won't try it in the future.
With the previous installations, I was
not able to use "select all" when in Manage Bookmarks to quickly remove all those Fx ones. I would not have been that irritated if I could have removed them easily. I also was not able to remove the default ones that come with Opera. In this current installation, after I deleted the bookmarks.adr file and Opera recreated it without the Fx bookmarks, I was then able to easily delete the default bookmarks like Ebay, etc. When I was in preferences, I noticed that I had a bunch of cookies from all those default Opera bookmarks that I never visited. I am glad I got rid of the bookmarks and those cookies.