In windows 8.1 , the "Close button" is a a few pixels to the left of the top right corner, so effectively when the mouse is at this location, single click won't close the window (maximized). (it is different from Windows 7).
I also notice that if I double click top right corner, it will close the window.
How to set it to single click to close ?
Edit : Here is a video if you guys don't believe me , the mouse came from bottom left went straight to top right, as it crossed the X button, the X button lit up, then as the mouse went passed the X button into the few pixels at very right border the X button then it went out
(note: there shouldn't be any space on the border, it just the capture program it adds to)