when i open my pc while power was flactuating,it didn't show me signal to the monitor. when power is normal i tried, it boots and every thing seems to be normal as before but no singal to the monitor and the mouse. i checked even changed every thing,fan,psu,ram,cpu and even i disconnectet all the patrs except video card and tried still no signal,but i only didn't use another video card.what shall i do?