check if u have inserted the ram(s) into the motherboard completely. if u have checked the ram and found nothing wrong with the ram connection, check if the cables r firmed connected to the hard drives. if hard drive is not what u r looking for, try to troubleshoot other parts one by one. u should be able to determine what is not working right.
if u have ruled out the hardwares failure, i will suggest reinstall ur os. althou it might not be very possible, improper installation of os can sometimes cause blue screen of death.
