graphics -puzzle

Hello,

I have a Toshiba laptop (quite a good one) which I now use mostly as a
desktop with a large external monitor external keyboard & mouse. It is set
up to use the external monitor exclusively, the laptop's own monitor is
always off. The graphics card is nvidea. I've used this setup for many
months without problem.

A few days ago, while I was working on the pc (I dont remember exactly what
I was doing) the laptop monitor suddenly switched itself on and some parts
of the display moved across to the laptop.

I have managed to get things back as they were (via control panel / display
settings , and using the nvidea controls as well) and all seems fine now.

Does anyone know what might have happened ??????

Thanks for all ideas

KK