Just a reminder, after a long hard winter, spring cleaning is just around the corner and your PC should not be left out. It is truly amazing what will accumulate on the fan blades, grills, heatsinks, and in general the inside of your case.
The fact remains that the average casual computer user spends 1 to 3 hours at the comp each day. Those of us that are on longer or run 24/7 need to be even more vigilant. All those hours converted into Air Flow means that for all the time your fans are running, they are transfering tremendous amounts of air through the system. Along with this AIR also comes dust and particles that clog the arteries of fans and heatsinks.
If you've been putting off this chore, now's the time to get cracking on this simple project. There is a short article at machinax about how to clean the mess up, it reminded me to get busy myself. Most of us do this on a fairly regular basis, but if not, your computer's insides probably look like this.