The following message has appeared on a number of occasions, after the screen went black and then returned.
"Display driver stopped responding and has recovered.
Display driver NVIDIA Windows Kernel Mode Drive, Version 259.36 stopped responding and has recovered successfully".
Is this a Graphics card problem, or a Windows problem?
I have not been able to find an answer on the net.
If the driver update suggested by Graphicool1 doesn't do the trick you might look to see if the graphics card fan is clogged with dust. It could be that the graphics card is switching off because it is getting too hot.