[JModason]

First and foremost, you need to give the inside of your computer a good cleaning. Disconnect everything, take it outside, and get all of the dust out of it. Vaccuum it out, blow it out with a duster, or pick it out by hand if you want, just get that dust out of there! Remember to get the fans nice and clean, so that there are no obstructions anywhere. After you've done that, reconnect everything and start it back up. If the noise still persists, then more than likely your hard drive is simply dying. The spindles could be wearing down, the motor could be dying, etc...I recommend that you quickly buy a new hard drive and transfer all of your important data to it ASAP. Hard drives are very cheap these days. You can get a 320gb drive for as low as $80.