Check to see if there is anything visible obstructing the fan.
I assume that the fan has got stuck with dust through the 4 years.
You can unscrew the plastic underneath the laptop and remove, this will enable you to check the fan a bit better. If you do a search for the service manual on google for the name of the laptop you can see how to easily gain access to the fan.
Depending on what model this can be changed pretty easy and cheap. However if you find that the fan does not spin do not use it for long periods of time as your CPU is not being cooled ( symptoms would be windows freezing ) - ultimately killing your CPU .. so i would recommend seeing to this problem pretty soon.