Dell laptop

Hi,
i have a dell laptop and it was used so i don't know how old it is. just a day ago i shut down my laptop and closed it. then today i tried to turn it on and it won't turn on!!!!!!!!!!!!!!!!!!!! the power button turns on for like 5 sec
and then stops.And when the power button is on, a little A with a lock around it flashes. Does that mean it is locked?????????????????? what button do i push????????? i already looked all over my computer for a lock button!!!!!!!!!!!!!!!!!!!!!!!! I love this laptop and want it back!!!!!!!!!!!!!!!!!!!!!! HHHHHHHHHHEEEEEEEEEELLLLLLLLLPPPPPPPP!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!