Continues strange sounds on my PC

Hello Everyone!
Hope you can help me. I have a problem with my pc, when I push the button to start it, the central unit starts but the screen shows nothing. Also, the most thing that made me feel chocked is that the pc make a continuous strange sound that seems to the sound when we have a message error but it begins and doesn't stop until I shutdown the pc using the push button.
Please help, it's urgent. Thankfully,
