Hp pavillion dv4 entertainment pc not showing display bt the power led glows

Hello,
My hp pavillion dv 4 entertainment pc running under win7 is nt showing display while i on it.al the led s lyk power led,keybrds led's n bluetooth glowr and i cn hear the fan also.bt the screen remains black nly.i tried to check if the battery is not okay by removing d battery and dirctly plug in.bt didnt worked,i found d same problem.and my battery dnt give back up.i use my laptop by direct plug in.what may be the problem? is there any issue with hard disk,procesor or motherboard!? plz suggest.