Paul

Can anyone help? When my pc starts up the it can take up to 15 minutes before any applications can open properly and during this time the fan is working it's guts out. The CPU usage is low when this is happening. It also somtimes starts happening somtimes for no apparent reason with the aplications either freezing or becoming incredibly slow and the fan starting up. Is the fan needing cleaned? And if so, what is the best way to go about this? Your help would be much appreicated. Thanks