The FIRST thing I do to a PC when it comes to my shop, is blow out the dust. After hundreds and even thousands of hours of run-time, the inside of the computer [especially the Power Supply and CPU fan and Heat Sink] gets 'clogged' with dust which prevents proper Heat Dissipation. As clean as your home may be, no computer is dust free! Electronics are dust magnets.
A common symptom of dust build-up, is that the fans seem to be loud. Some even make a sort of 'screeching' sound. Another symptom of dust buid-up and over-heating is PC running slow and even frequent shut-downs or restarts. The exhaust from you pc or laptop should be warm, not hot like a hair dryer.
Pull the cover off and blow it out with a can of air. Do it outside, and try and blow the dust away from the drives! A little dusting can go a long way to prevent further, more expensive problems. If your computer is slow due to poor air circulation, there is little else that can be done to speed it up.
Using a custom vacuum attachment made from a coffee can lid, and a can of air to remove dust from laptop or net book WITHOUT disassembly.