Today I bought a new Dell monitor and was planning to use it as an external monitor with my Dell Laptop.
When was sing it in Extended mode, everything was working fine. Mouse pointer was moving between both monitors flawlessly.
But when I tried to use external monitor in 'Projector only' mode, my laptop monitor started flickering(I was expecting it go off) and mouse disappeared from external monitor.
Simple Fix -
There was a third unknown monitor present in Display settings.
(Control Panel\Appearance and Personalization\Display\Screen Resolution)
I just deleted/disabled that 3rd unknown monitor and Bingo!! Laptop screen went off and mouse pointer appeared on external monitor.
Similar solution for Ubuntu can be found here
