Computer makes clicking noise when I turn it on?

My boyfriends computer recently started this weird thing, where every time he turned it on, or rebooted it makes a clicking noise for about 3 minutes, then stops, and then when it gets to the sign on page his thing flickers, like where he puts his pword in to sign into his computer, it flickers? it will disappear then come back, and then do that tons of times in a row really fast and he has to push F8 a a lot of times for it to reappear and stay there? What does this mean?