I put a new cooling fan in our home computer yesterday. It's a Gateway 838GM desktop computer, that has mostly been good to us - aside from needing the mother board replaced last year. But the little cooling fan in the back started making outrageous noise about a month ago. It was somewhat intermittent at first, and I could usually get it to stop if I beat on the back of the case in just the right spot, but... finally it needed replaced. And it was easy. I even did it myself.
I took the side off the tower and there are four screws that hold it onto the inside of the back. There is just one set of four wires that plugs into a 3-pin slot. I took the old one out and googled what it said. It is a Foxconn Model PV902512P, 90x90x25mm 4-pin DC Brushless Fan. I came across a company called CWC Group that had those fans for $8, and shipping and handling was $6.50, so I ordered one. It came in the mail in 2 days.
So I just took the old one out, screwed the new one in, plugged her in, and... presto... we have a quiet fan again. So nice.