as when i on my computer, it show "No Signal" from the monitor.. but i check the cable and it was plug in tight, so what happen to my computer or how can i solve it?
You could have a bad video card or bad onboard graphics chip if running onboard video. If you have an expansion card installed first try reseating the card down into the slot fully to see if that is lifted up or another card.
If this is on a laptop or premade desktop with onboard video you would need to take it in for service. When an onboard chip goes the other option is to install a separate video card whether the PCI or PCI-Express type.