I have just finished building my first pc. When I do first boot, there is no display, but it worked when I tested just the mobo/video card(7870)/ram outside the case and it was connected with vga cable to my mobo. I also have display when I took out the video card. Is this because I need to connect my video card to the monitor? The reason I havent is because it needs dvi/hdmi and i only have vga cable atm.