I just built a pc and it runs great, but it boots very slowly. I get the desktop and one or two icons on the system tray, but it just hangs. After 1 or 2 minutes the HDD kicks in and it finishes booting. It usually shuts down fine but the other night I shut it down and left, and the next day my gf said that she had to shut it down by the power button, and she said it made a loud buzzing sound, which I think was probably the HDD. What could be causing this??