This is why..
Even in the cleanest of domestic and commercial environments, a computer will manage to attract dust. A fair amount gets blown through the system as can be seen if you look at the wall or partition behind the case. Some of the lighter particles travel up with the warm air and are caught on the wall just above the case. Heavier particles fall to the floor. Go take a look, and remember that this is only the stuff which escapes all of the catchment areas in the computer case.
Power supplies always suck air OUT of the case, which means that there has to be some way of letting air in. If you look at the front panel on your tower case, you may notice a grille at the foot of it. This is generally the official entry point for air. Sometimes, you will see other areas of the case which have been perforated to allow for air in and out. The trouble is that air does not recognize official entry or exit points. Turn your tower upside down and look at the gap between the front panel and case skeleton. See it, all collected around the wiring from the panel LED’s?
The gaps around floppy and optical drives are fair game for the ingress of air, as are the drives themselves. Floppy drives will cease to be of value when dust collects on the read/write heads. In most cases, the top can be removed from a floppy drive, and the dust build up can be removed carefully. Not so with optical drives. Removing the top reveals a circuit board and little else. You can use a CD/DVD drive cleaner disc on these, and if you are lucky, it will clean the dust from the laser. Well, at least move the dust away from the laser for a while at least.
Let’s go further into the case..
The video card, if regarded by the manufacturer as a performance part, may have a fan attached to it. Early types have what looks to be a regular, albeit small, fan attached over the video card’s processor. The fan pulls air onto the processor and escapes through the sides of the fan casing. That is the theory, and for AGP video cards works well enough. AGP video cards are always set away from the PCI slots, thus allowing decent clearance between the fan and any PCI cards in use.
For PCIe video cards, the picture does not look so rosy because PCIe slots are very often in line with PCI slots, and spaced about the same distance apart. If you have a couple of PCI cards installed in the average system, you will have used up all available slots and the one nearest to the video card will hamper the free ingress of air into the fan intake. Needless to say, this fan will eventually clog up and cause overheating of the video card. This may lead to odd behaviour by the graphics system, and will always help with overheating within the case.
At this point, your hard drives are already running hotter than they should. If you have one of the thinner hard drives, Maxtor 40gb for example, which have a tendency to run hot anyway, it could very easily fail and without giving notice. Mounting two of these drives in the average case is asking for trouble. When buying a case, ensure that hard drives can be mounted such that they are not in close proximity. Insist on taking a peep into a case BEFORE you buy it.
Onwards, upwards and back a little..
We have arrived at the CPU fan and heatsink assembly. The fan may still be turning, but is it pushing air through the fins of the heatsink? It could be if it were not for all of the dust which has collected there. You would think that this fan would be turning quickly enough that no dist would get caught here, and you would be right were it not for the fan case moulding. This is where dust first collects, and the rest is history. Removing dust from here is not always as easy as it should be. Sometimes it bakes into a mud layer which will require that the fan assembly is removed from the heatsink. Sometimes, the fan will not separate from the heatsink, forcing the removal of the entire assembly from the processor and socket. Before reassembling, you have to clean off the old thermal paste and put a dab of fresh stuff on. If you don’t have thermal paste, do NOT remove the whole assembly.
The main culprit..
The power supply is what sucks air and dust into the case, and it doesn’t escape the rigours of dust build up. Removing the top of the power supply will break the manufacturer seal and warranty, and is not a good idea anyway as power supplies can and do hold residual power for some while after shutting down. To clean it anything like thoroughly, you should remove it from case and blow compressed air through it. I do it while the power supply is running. It helps get the dust out of the unit, but I would not suggest that you do the same.
The fun is not over yet..
So far, you have removed and cleaned both sides of the case, the optical drive(s), the floppy drive, the hard drive(s), the CPU fan and heatsink, the video card,all cables and the power supply. Any PCI cards will also have been removed and dusted down lightly.
Oh, am I slightly ahead of you? You have to take out all of the parts to enable cleaning the dust out of the case. And don’t forget to wear a dust mask and something old. This is a messy but vital job.
Clean the outside of the case and the front panel with Isopropryl Alcohol before re-assembling, and then start to put it all back together. Front Panel first, then power supply, optical drives, hard drives, cables etc. This fun activity could take two hours out of your life, but extend the life of your computer no end.
It may also put an end to strange behaviour, noises, and crashing out.