blank screen ,drivers for onboad cards?

hi!
I have two questions: I got blank screen, after replaced the video cards and memory and even power supply it is still not thing on screen when power up the system, I switched the monitor as well, the green light is on for few seconds and turn yellow, and the same thing happens,
second, could you please tell me where and how to get the drivers for ON BOARD sound card and video cards? when I upgrade the bios do I get them automatically? I am really appriciated for your help.