Need fan help...getting increasingly louder

I am certain it is not the cd drive, as that died a while ago. I just ordered a replacement which arrived today. As to the questions about the fan and hard drive, I do not know. I took the cover off the mac and had to disconnect the power button to do so. I also had it unplugged. 🙂 I am not sure how to check the things you mentioned. I will say that the IT folks who work for the county that my mohter-in-law works with say many computers and other electronics were damaged by having things shaken loose. I am wondering if that may have happened with my computer or if the fan has died of old age. I am not a computer genius, but I can follow directions pretty well. Any help you can give will be much appreciated.

OK. I turned it on with the cover half off. As far as I can tell, the fan in the back, at the bottom (not the top, like I said before!) is the problem. It is a big white fan. It makes a harsh noise, but appears to spin freely. I cannot see any other fans, but I did not open anything. I am going to replace the cd drive. If the noise goes away, I guess that will have fixed it. But, I really think it comes from the big white fan in the back. Your thoughts?

I finally fixed my fan problem! I was able to follow some directions on how to lubricate your fan and it worked like a champ! Now have my fan, hard drive and optical drive all fixed up. It is like a new computer. Thanks for your advice and for anyone that needs to, you can get a fan online if yours dies or you can try lubricating like I did.