Also, after you download super_disc.iso you need to extract the ISO file and that's what you copy to the CD-R. I used WinRAR to do the extraction and I think I just copied the folder created by the extraction (and the files contained in it) to the CD-R. (Originally I had tried copying the downloaded super_disc.iso file to a CD-R and when that didn't work I reread the directions at http://www.multi-region.net/oppo_bdp-83 .)
The instructions to "extract" the file are misleading, at least on Windows 7. The downloaded file is already a .iso file. I can open it up with 7zip and see the folder called SUPER, but because it is already an iso file, extracting that would be a mistake.
Instead, at least in Windows 7, just right-click on the downloaded file and it has Burn Disk Image as an option. Select that, and it creates a proper copy onto CD-R.
My problem was just that I used DVD-RW the first time.
This time, the Oppo didn't give me the unrecognized-disk error.