If the fan is clanking/clicking it needs to be replaced, a whine is an indication that the fan will be failing soon and will need to be replaced.
In general if the fans are spinning really fast it means that the system is getting hot and needs cooling. make sure to clean out your system regularly. http://www.pctechbytes.com/DIY/maintenance.htm
You may need to get another fan or two to install in the system to increase air flow, or move the system to a better ventilated area.