Frankfurt  - Crumbs, fingerprints and dust bunnies: every computer gets dirty. And the dirt is not just unattractive and unhygienic; it can also shorten the computer's life span if, for example, the fan is clogged up and cannot cool the components. Cleaning is fast and choosing the right tools for the job is half the battle.

The keyboard, monitor and fans are particular dust magnets. Computers that see heavy use quickly show wear and tear. This can include crumbs, nasal hair and even nail varnish can smear the monitor, if it is touched frequently, says Dirk Plaehn from EDV-Clean-System, a service provider situated near Hamburg.

Yet users are often unaware of the fact that their power supply and cooling fans inside the computer can also become dust-laden. The internal heat is then carried away less effectively. This can lead to crashes, and in a worst case scenario complete failure of the components due to overheating.

"The interior of the computer should be cleaned out at least once a year. Input devices and monitor once a month or more, depending on the level of soiling and cleanliness tolerance," advises Markus Schuetz from PC maker Dell.

Surfaces that are relatively clean require no more than a quick swipe with a dry microfibre cloth. For more serious soiling, standard household cleaners may only be used in some circumstances.

"Rinsing agents and paper towels are unsuitable," Dirk Plaehn warns. While they are good for cleaning dirty dishes, they are not good for heavily soiled keyboards. Solvent-based liquids are no better. While they will seem to do a good job of cleaning, they leave the surface porous and even more susceptible to dirt.

Plaehn recommends special plastic cleaners to remove sweat and grease from the keys. These can often work miracles. Heavy users should not expect to restore their keyboard to brand new appearances.

"If used heavily, it's normal for the matte coating to rub off. That makes frequently used keys appear somewhat shiny," notes Markus Schuetz.

Any cleaner used for the keyboard is also suitable for the rest of the computer's surfaces except the monitor. Only cleaners specially intended for the display should be applied. Wet wipes for cleaning spectacles are also acceptable. The first step is a mechanical cleaning pass with the vacuum.

Compressed air cans are an effective way to remove dust and dirt from the grooves on the keyboard. Compressed air should be used with care, though, warns Markus Schuetz from Dell: If applied incorrectly, it can blow particles into unreachable spots. A simple brush with soft bristles or a hair dryer can also serve as a compressed air substitute. If working with a hair dryer, be sure to turn it to cold air. Otherwise it can deform the plastics in the computer's casing.

Vacuum cleaners can also be used on the interior of the machine. The fan blades and other computer parts like the motherboard and plug-in cards can also be dusted off. Opening a PC housing is normally no big deal.

Laptops, however, are best opened by trained professionals. "Opening it on your own can void your warrantee." Laptops are also very difficult to bring together," Dirk Plaehn reminds. As they are built more compactly than desktop computers, there is less danger of dust getting in.

INFO BOX: Fundamentals of cleaning the computer

There are several basic rules to learn to ensure that your cleaning session won't actually damage the computer, says IT cleaning specialist Dirk Plaehn. The computer should never be cleaned with liquids. Spray the cleaner onto the cleaning cloth, not the surface itself. This prevents drips from flowing into the electronics.

Potential lint sources like paper towels are also taboo. Otherwise you may end up introducing more dirt than you actually clean out. Make sure you turn off the computer and pull out the plug before starting a major cleaning effort. If the interior of the computer is to be cleaned, then the user should first ground herself, such as by touching a metal radiator. This prevents electrostatic shocks from hitting the sensitive devices. (dpa)