I have a GeForce GT 640 video card, but by default the screen flickers badly. And if I change the refresh rate to 59 Hz in NVIDIA Control Panel manually, everything is OK. I don't know why. Now the problem is, if the system restarts, the refresh rate become 60Hz, then the screen flicker is flickering. I need to change the refresh rate again. Can I keep the refresh rate to 59 Hz? Or it would be better if the screen doesn't flicker at 60 Hz.