Thanks for the response.

I found that the two monitor entries were for the monitor output and
the S-video output. I had forgotten about the S-video.

I never found the real cause for the problem, but I did discover that
the video driver had a newer update available from Dell. After
installing that update, I could now perform the actions to synchronize
the screen and the monitor output as described by the instructions and
Dell KB articles. I now have the problem solved.

Thanks again.