Greetings, I have Dell Inspiron 8600 which seems to be in great shape except for one thing. After I use it for a certain amount of time a loud noise begins, which sounds like a fan, and slows down the processing. Before the fan starts the speed of the computer is normal, but then it gets incredibly slow. Also, if the more applications I run the faster the fan starts to run and slow things down. Is this a fan? Is there anything I can do about this? It wasn't always like this; it just started doing it a few months ago. Many thanks.