|There's probably nothing wrong with your monitor. |
If you have both onboard video and a video card in the slot, make sure you have the monitor video cable plugged into the video port on the card in the slot - in most cases you get no video from the onboard video port when a AGP or PCI-E video card is installed in a slot.
E.g. on a desktop tower case, the onboard video port is higher up in the same place where most of the ports are, the video port on a video card in a slot is lower down in a slot space.
Keyboards don't necessarily have an led that lights up while booting. E.g. if enable Num Lock led while booting or similar is disabled in the bios Setup, the led for that won't light up until you press the Num Lock key.
Make sure the plug for the keyboard is in all the way before you boot. Never unplug or plug in a PS/2 keyboard while the computer is running.
If it's a PS/2 keyboard it must be plugged into the purple PS/2 port, not the green one