Bios Setting

I was messing around with my bios configuration and i disable the plug and play configuration and now my laptop monitor doesnt work, when i start the computer the monitor screen is black and a message in the monitor screen says that the monitor is not conected to laptop, how can i restore the defaults settings or configurate the plug and play again? remember my monitor is not linking to pc! help! I have a GATEWAY 400SD4 and i took the original laptop monitor out and put a desk flat lcd screen monitor on .. what can i do ?