Problem in Monitor resolution after a driver update

I normally always keep my PC in hibernate mode and only rarely I do restart. This time I had updated a few drivers including COM port drivers, Webcam and other graphical drivers. It prompted for a restart but I cancelled it. Finally, I shut down it properly. But this morning, when I turned on the PC I could only see basic colors and very bad resolution, looks like basic graphics. All the images are of lower resolution. Worst thing is I am not getting how to change the resolution too. I have a 21 inch wide, ACER monitor. What might be the problem? Shall I attempt system Restore?
