Nvidia graphics card problems with Windows 10

I have an nVidia GT650ti graphics card on my PC, which worked perfectly with W7.

My PC has now been upgraded to W10 64bit and I have installed the latest, correct, drivers for the graphics card. Everything is ok until I shut down the PC and then boot it up the next day when I find that the screen display is a bit 'washed out'. I increase the contrast setting to 75% and everything is fine again. The next day I boot it up again and the display is 'washed out' as it was before so I increase the contrast to 78% and it's good again.

You can probably guess what happened the next day....exactly the same and so on up to today where, once again I have had to increase the contrast, which is now at 84% to correct the display.

Clearly something is not right and what happens when I get to 100% contrast and the screen still looks washed out?

Any ideas?