This is weird.
 

I set up my laptop so that I could run an S Video cable from it to my TV. It was (for the most part) already set up for this-I just had to click on something to tell the laptop to output the video to my TV set. I did it so I could play those old Christmas shows in my living room (see X-Mas video thread) and let my kids watch them.



Now my cursor goes off of my screen when I move my mouse to the right too far. I know it isn't just a sliver of my screen being non-viewable. I've roughly timed a few trials and it is actually covering real estate when it disappears.

I use that a lot and you have to play around with clone and the side by side settings.

You probably in the side by side mode which makes an extended desktop to the right or left, and maybe up and down.