Hi GailGN,
First, you need to figure out if this is a fan or CPU usage problem. There are times when a Windows process will run out of control and consume all of the CPU's processing power, causing it it heat up and the fan to run out of control. The way to check this is with Process Explorer. Search for and install that utility, then run it in the background. If you see anything running out of control, use Process Explorer to kill the process and see if the fan settles down.
If on the other hand, you see no such process, then replace the fan.