if you acer has the e button for acer emanager , press it and then click acer settings
you click boot options , then there is a selector to have the fan enabled,
if overheating  is the problem your fan should now run  full speed.
also ,  find the fan grill located at the side and rear of the computer and blow through it , the fins get clogged with dust  and this prevents  cold air getting in , use a hoover if need be
                
 jase
                
 December 2007