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	Cleaning A friend of mine had an interesting problem with his Windows NT system at home. It would run fine for a few hours, then crash. It didn't matter what applications he was running; he even let it sit without even logging in. Two or three hours after booting up, it would crash. When he rebooted, it would crash again. Only if he let it sit for a few hours would it boot up and run --- for an hour or two. Well, to cut the story short, eventually he took the cover off the machine and found that his CPU cooling fan had stopped. Replacing it with a new one was all the fix he needed; no more crashes. You need to look inside that box on occasion. Not much, just once or twice a year. The computer is a precision instrument, and it needs to be cleaned and inspected. Dirt? Yes, computers get dirty. In fact, whenever I see an intermittent problem on a computer, the first thing I suspect is dirt. You have a fan in the power supply blowing hot air out. This means fresh air gets sucked in through the computer case, and that air carries dust with it. Even in a clean-room, there will probably be some dust, but in a home office, it will be inescapable . The dust settles on the components. It insulates them, so they don't cool as well. As they get hotter, their performance changes. Transistors change their values spontaneously. And that means data in memory changes, and CPUs perform the wrong instructions. Anything can happen. If the environment is humid (say, summer in Florida), the dust may get damp and cause low-voltage short circuits. This can send random signals to the components, which then do unpredictable things. Again, data in memory may be changed, anything can happen. The dust also works into the bearings of the fans and eventually stops them. The components get hot, change their behavior, ANYTHING can happen! Cleaning up Fortunately, this is easy to prevent. For most of you, a simple cleaning once a year is all you need, though some sites will need to clean more often. First, back up everything. I know, all you're going to do is a little cleaning, but accidents happen, and you could drop a screwdriver on your hard disk, or even drop the hard disk. Play it safe, back up . Now shut down the system and unplug it. If you don't have plenty of room to work, disconnect all of the cables and take the box to a large table. Now take off the cover and ground yourself to the box. You can pick up a grounding strap, which wraps around your wrist and clips to the computer, for five or ten dollars. It's a very important tool, since cleaning the machine will generate static electricity which can seriously damage the chips. Use a small paintbrush (1 inch wide is good) to dislodge the dust on the components, then vacuum it off. You can get a mini vacuum cleaner designed for computer work, or small attachments for a regular vacuum cleaner. Use an attachment with a brush on the end to suck out as much dust as possible. You should take off the CPU fan so you can get into the heat sink, and you will probably have to remove cards to clean them. After you have vacuumed out the dust, reverse the cleaner and blow off the remaining dust. Then check to make sure you got it all, and clean up any dust you missed. Don't blow dust off with your breath; it's moist air, not good for electronics. Also be careful not to drip sweat into the machine. The salt will corrode it and short it out. If you had to remove cards, check the contacts before putting the cards back. If the pins are dull or discolored, take a soft pencil eraser (art gum is best, but never use a hard or abrasive eraser) and gently polish the pins. Don't touch them with your fingers, and don't touch the components on the card any more than you have to; it's best to handle only the edges of the cards, so you don't get corrosive skin oils on any metal. Gently replace the cards in their slots. Before you reattach the CPU fan, try spinning the blade. It should be smooth, and it should coast freely. If it does not, it's starting to fail. Replace it. Also check the fan in the power supply in the same way. If it's failing, replace the power supply. Don't try to replace the fan alone unless you know what you're doing; the insides of a power supply can give you a dangerous shock even when it's unplugged. Plug everything back in and power up. Make sure the machine boots. If it doesn't, back up and find what you did wrong and correct it (see the Making Changes article). Once you can boot successfully, power down, put the cover back on, and restore the machine to operation. Other Cleaning Floppy drives, CD drives, tape drives and other removable-media devices also need periodic cleaning. Corrosion and foreign particles build up on the read/write heads and cause errors, making the drive unreliable. You can buy cleaning kits for all of these. Make sure you get non-abrasive cleaners, and make sure they are compatible with your devices. For example, I have a good CD drive cleaner, but it won't work on a drive that uses a caddy. These cleaning kits come with instructions, so just follow them. The ball in a mouse will pick up dirt and transfer it to the rollers inside. Eventually the build-up will cause problems. You can easily clean off the rollers by removing the ball and rubbing the rollers lengthwise with a pencil eraser. Don't press too hard or you may break the roller. Most keyboards use membrane contacts; these are sealed sheets of plastic, and are waterproof. Dirt and wetness don't bother them much. Still, it's a good idea to clean them out now and then, especially if you eat at your computer. Just unscrew the bottom, carefully lift off the top, and use the paintbrush-and -vacuum procedures described above. Of course, power down the computer before you do this. Dirt on the keycaps won't affect the operation of the computer, but it's pretty ugly. You can clean it by gently rubbing with a cloth moistened with a mild liquid cleaner like 409. Do this with the computer off, and if there is any chance you let liquid dribble inside, open up the keyboard and make sure it is dry. Windows NT Likes Clean Computers Many people complain about frequent crashes of Windows NT. I keep my machines clean, I make sure the "little things" like the fans work, I keep my files defragmented and my partitions at least 35% free. It hasn't crashed in at least a year. It's not a coincidence. Lance Jensen Technical Support Manager Executive Software International, Inc. If you have any comments about this article or any requests for new technical articles e-mail
	Executive Software Europe