iphone will not turn on

Hey there

I am not sure if somebody already answer that or not I have iphone 3gs.by mistake I drop it on a bare floor it was tile floor. After that it will not turn on unless I plug it in a home charger. and hold both power and home button then first i get the apple logo then it I get home screen and it keep saying searching for cell phone even though I didn't signup for any cell phone service signal it will stay on for 5 or 10 second then it goes black but it will not do any thing.

last night it happend this morning when i plug it again. same thing apple logo came on thne screen stay on for 10 seceond then goes black and last nigh battery was full this morning it was not it was in charging status but it won't do any thing. If I plug it in computer nothing happen it will not show up I TRY winxp, vista 64bit and windows 7 but result is same Itune and computer both will not detect it . Is there a way to fix it or it is dead I don't know it is a hardware problem