Seems it's an NVidia incompatibility problem after win10 Creators Update.
Have found solution as given below:
"
I knew that nvidia updated the same date as windows 10 creator mode arrived, so I went into that control panel. There, I found an option to override system settings for screen size etc. So I choose "adjust desktop size and position"---> "full-screen" "override scaling mode set by games and programs"."
It's working now.
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