Damn computer noises...

[Jason1]

So I had that little fan problem awhile back, when my fans (or maybe it was just one fan, who knows) made a helluva lot of noise while booting up then quited down shortly after. I learned to live with that, but now something inside there, probably one of the fans, is making a higher pitched constant whine...never stops. It's not terribly loud, but definatley enough to annoy beyond belief. Is there a way of pinpointing this problem, what or what fan is causing it, then fix it, even if that means buying a new fan?