PC making weird sounds when turned on?

Hi everyone. When I turn on my computer (windows vista) it sounds like a chainsaw. This used to happen for a couple of weeks around 6 months ago. I didn't do anything about it but now the sounds have come back again. The noise stops around the point where I am prompted to enter my username and password. I have also had the "grey screen of death" over the past few days, which automatically restarts the computer and is quite scary. Is there any chance that the noises and the grey screen of death are related? If so, what should I do? I'm really worried and would really appreciate your help.