My main computer is an hp zv5000 - it uses two heat pipes with heat sinks and two fans to cool the processor. Through use, those heat sinks (copper?) and pipes collect quite a bit of dust reducing the machine's cooling capacity.
If you don't have this specific machine, not to worry. Just use some common sense as the basic idea is the same.
Step 1: Tools and Supplies and First Step
You'll need two things:
Q tips and a screw driver
First Remove your battery (possibly a duh! step, but just being thorough).
Unscrew the Ram cover - to make removing the rest of the case easier.
You'll need to remove the plastic cover just behind the battery 'cave' - remove any required screws and keep track of where they came from (some of mine were longer than average).
Step 2: Removing Fan Ducts/covers
Remove the plastic cover carefully. It should not stick - if it does, go back and look for a missed screw.
Now we have the lovely task of removing some tiny screws that hold down those two fan ducts/covers. I used a #1 screw driver with a magnetic tip. This saved my butt as I would have easily dropped/lost one of those screws.
Step 3: Clean
Use your Q tip and wipe away any dust etc. off the fan blades and from the heat sinks. I guess you could use some compressed air, but I did not have any on hand and was able to get everything out.
When you're done, reassemble.