After uncommenting
disable_overscan=1
follow my lead. In the link, http://elinux.org/RPiconfig when you search for Video options, you'll also get hdmi_group and hdmi_mode. For, hdmi_group choose 1 if you're using you TV as an video output or choose 2 for monitors. Then in hdmi_mode, you can select the resolution you want from the list.
I chose :-
hdmi_group=2
hdmi_mode=23
And it worked.
