Q: the screen is black

Hi there,

Well i have a iPhone 4s bought it from a friend, it was working all good until yesterday the screen went black after a continous vibration, and nothing works since that, i tried to swich it off and then on, but nothing happened, and the weired thing is when i made a call, it's like it is on, but no ring tone on the iPhone. after calling the phone i pluged it with my PC but no reaction, the same as the charger...

So what's the problem and how can i resolve it?

Please let me know what i can do as soon as possible, i don't want give it to some one to fixe it.

Best,

Nassim