Pc problem

[Kotel]

Hello all..i have a problem...3-4 days ago i turned off my computer (normally)and the other day i tried to turn it on but i couldn't.The whole pc works normally but the screen is always black(it works normally it has the light on)when i try to close the pc or reboot it i can't the buttons don't work i can only turn it off from the behind....sorry for my bad english but if u have any ideas plz help me...tnx in advance