Avenged Vampire

My PC hasn't worked in a year and everyone has given up on it so i decided to ask on here. all of the internal parts have ben replaced except the hard drive. It now boots up to a point then a blue screen flashes and it restarts. After a couple of restarts it cuts off lik its lost all power and im back at the start. All of the internal parts are new and I've tried with a different hard drive with no sucess. Any surgestions???