You will now have a file called OpenGLid.INI in your RB folder.
Edit this and set InitFullScreen to 1. Probably worth setting MipMapping too.

Thanks for the reply. I now have the full screen. 😀 However I now have the return of the no sound problem. I have: (1) deleted the file brprefs then started RB 3D and set the preferences (while sound played) (2) Alt + Tab out of RB and set the brprefs file to read only. (3) returned to RB and found sound still working. However, if I leave the game and then restart Red Baron I no longer have any sound. 😕

Deja Vu all over again...

Close RB, go to your RB folder and delete RBPREFS.DAT. Then, open RB and set all your favourite preferences but don't fly, and don't close RB. Press Alt-Tab to get back to the desktop without closing RB, go to your RB folder, right-click on RBPREFS.DAT (Red Baron will have re-created it), go to Preferences and set it to read-only.

Now, note the time. Go to the game screen just before you actually quit and do nothing for a few minutes, then quit. After you quit, check the timestamp on your RBPREFS.DAT file.

Is it set to the time you set the READ ONLY attribute?
Or the time you quit the program?

Nicht Sehr Gut,
The time stamp is set for the time when the rbprefs.dat file was completed. I waited there for three minutes before ALT+TAB out of the sim and setting the file to read only. I then went back and flew for four minutes before exiting RB. When I restart RB 3D there are no sounds but the preferenceces are still set as I left them. Do you have any idea why this occurs if the file is read only or what else I could try?
Thanks,
Jim

Only heard of one other RB case this stubborn:
showthread.php?threadid=983

and all I can suggest is the same as there... to set up a batch file that copies a good RBPREFS.DAT file on top of the corrupted one from a backup directory after starting each game.