i bought benq xl2420t 24" monitor to replace my dell 20" dell monitor.but i got problem with resolution .that i won't full screen on its full resolution(1920*1080).i have tried changing cables that it only works on HDMI and shows no signal detected when connecting DVI CABLE .I am using dell motherboard with 6gb ram and ASUS HD7770 DDR5 graphic card, i3 processor.somebody give me suggestions to get rid of this problem...