Hi Mansu

I have the exact same problem  with Dell E6420  it goes to Dell Logo  i can use F2  and F12  ,

I does detect the hard Drive,  i have change the bios to default ,  Still no help

I have Pressed F12  , and chose dignostics ,  allso boot from Cd  still blanck screen after that

I have tried external display its still the same

Thanks

Harinder