Acer travelmate not starting up

my acer travelmate 5520g is not starting up i cheak every thing like cooler fan cmos battries etc but also not working when i try to turn on it just response as normal like cooler start cd run and other indicator blink and immideatly fan stop just after few second fan start running and then laptop shut down automatically without any display in screen nither any bip sound . i am fustrating and think in trouble please can you help me i will be very thank ful. please