computer power on, fans running but nothing happens on screen

sancubes

Honorable
Jan 12, 2014
35
0
10,540
here is my system specs
AMD phenom ii x4 980
ASUS A4M88 M LE
Corsair XMS3 DDR3 RAM
Cooler master extreme power plus 500 W
AMD HD 6670 1 GB DDR5

its 1.5 years old system

my problem is
when i strart my system by pressing power button, it gives beep sound and starts normally, but when i try to restart it through startup menu, computer powers up but no beep sound and nothing on display

i tried to solve this problem. i removed my graphic card and connected the display with HDMI port of motherboard. then i started and restarted my system. it ran just fine.
so i thought my graphic card is culprit. but i am able to play game and do work on my PC with my graphic card when i start it by pressing power button. if my graphic card has been faulty then i wont be able to do that right ?. but it is not able to restart through startup menu.
do you think what is the problem my graphic card? motherboard? or power supply?