Hmmm. I think we need a bit more info from you here.
"Noisy" is all relative isn't it? Do you mean like... jet engine noisy? Or like.... someone annoyingly whispering in your ear noisy?
If you are talking about the jet-engine kind of noisy, you say you replaced your heatsink/fan on the CPU. Are you SURE that this was the fan making all the noise then? Maybe it is a different fan that is making all the noise?
What heatsink/fan did you put in?