I am using hdmi Cable..
Well THERE's your problem! (Aside from your grammar, overpriced, badly built computer, and belief that a closed-loop liquid cooler is better than an air cooler.)
HDMI is a TV gimmick - just like how 720p is supposedly "HD."
It isn't, contrary to what everyone believes, ANY better picture quality than DVI - it's just DVI with sound... and less image options.
You need a dual-link DVI cable - the one that has pins with no gap.