After searching, I thought to change the RAM in different memory slot ( Dual Channel DDR3) and my PC started normally and display as well. So, i restarted my pc after 10 minutes and all things did well. But when i shut down and i press the power button to turn on my pc did not start. So, i made the same thing and nothing changed. In other words, when i change the RAM in different slot my pc works and my monitor is working. Without changing it in another slot, when i restart it everything goes fine, but when i shut down and press the power button to turn on, my monitor does not work and the front fan too.... why?? there is no beep or motherboard LED's ! I built my PC in 2014 CPU: Intel Pentium G3258 3.2 Ghz PSU: Corsair VS Series 450 WATT MOTHERBOARD : Gigabyte GA-Z97M-D3H RAM: Corsair CMZ8GX3M2A1600C9 Vengeance 8GB ( 2x4GB) 1600 MHz SSHD: Seagate ST1000DX001 1TB 3.5 DESKTOP SSD: Samsung MZ-7TE120BW 840 EVO I do not have Graphic Card. PC is running Windows 10 Pro Version 1903 When I change the ram I mean that i shut down PC and i unplug supply cable, all usb cables, LAN cable, and VGA cable. There is nothing connected to PC. Later, I press down the tabs at either end of the slots and i change the ram. For example by grey slot i install it to the one black slot. So when my computer turns on but Displays nothing i remove it from black slot to other grey slot. My Motherboard has 4 slots. ( black, grey, black, grey). In the end, I plug all cables and my PC and my monitor work fine. Please help me! Thank you!