Step By Step Cleaning
First, I unscrewed the four brass mounting bolts holding the CPU carrier to the motherboard.

I was then able to use the plastic CPU carrier to lift the entire assembly out of the PC. This helped ensure that all the mechanical stresses were on the plastic carrier, and not on the CPU or its bond to the heat sink.

You can remove the carrier, CPU, and heat sink all at once, as shown here; or leave the plastic carrier in place, and remove just the CPU and heat-sink assembly. (click image for larger view)

Removing the plastic CPU carrier, I now finally have easy access to the CPU/heat-sink assembly for cleaning.

Again, this is nearly a worst-case scenario: Most newer PCs offer much easier access to the heat sink and surrounding area without having to remove either the heat sink, CPU, or both. Your job will probably be simpler and less complicated than what I'm showing you here!

After setting aside the plastic CPU carrier, I then had easy cleaning access to the CPU/heat-sink assembly. (click image for larger view)

You now can see that a significant portion of this heat sink was clogged by dust: there's no way it was doing its job. If we hadn't cleaned it, this PC was headed toward serious overheating and a shorter lifespan.

Once again, our trusty cleaning cloth helps to remove the worst of the dust from the heat sink. (click image for larger view)

This was the dust and dirt made inaccessible by our test system's old CPU design. Now, we can clean it properly.

This is the part of the system blocked by the CPU. With the CPU removed, the whole area now can be cleaned. (click image for larger view)

Work to loosen the dust and dirt you see so it can be blown out later. Ordinary cotton swabs do a good job in nooks, crannies, and other space-restricted areas.

Plain, dry cotton swabs are great for cleaning inside places too small for fingers. (click image for larger view)

When you've gotten most of the dust and dirt loosened or removed, use "Dust-Off" or a similar "air-in-a-can" product. These inexpensive products can help your cleaning immensely by providing highly controllable, highly directional, very intense bursts of dry, filtered air. The cans usually come with a long plastic nozzle that's ideal for working inside crevices and hard-to-reach places. Many brands of "air in a can" are available; your local office-supply or electronics store probably stocks several.

As shown in Photo 30 (below), use a cotton swab to prevent fan blades from spinning freely as you blast them with compressed air: This prevents the fan from spinning like a pinwheel, and possibly over-revving enough to damage the bearings or motor.

A blast from an 'air in a can' product will just about complete the cleaning job. (click image for larger view)