Laptop not working

Hello

A while ago I turned on my laptop and for the first time something unusual happened. No screen just the fan running loudly and continuously. I attempted holding down the power button but it made no difference. 

I disconnected power to the laptop but the fan kept doing a while. After that it the fan began running on and off periodically. I tried the power and d buttons but that did nothing. 

Any suggestions. I have a Lattitude 5420.