Every month or so one of my friends takes advantage of my technological expertise and calls me with a problem -- a broken hard disk controller, a dip switch, or a new sound card that doesn't want to install. Can I come over and fix it?

I don't want to, of course. I try every conceivable dodge -- taking the phone off the hook, the universal choke sign, pulling the kids out of school and moving in the night.

But eventually they wear me down, and I find myself over at their house, computer guts dangling every whichway, and my arms sunk deep in cables, ribbons, chips and screws. The look of faith on my friends' faces is totally unwarranted. I never, ever fix my own computer. To be honest, I don't know how they work. But some people you just can't get through to.

Anyway, I have devised a few dos and don'ts to observe in the delicate business of poking aroiund inside other people's equipment:

First, get all spouses out of the room. All day long he or she has been giving your friend hell for spending the furnace money on a computer in the first place. (That's probably your fault, too.) Spouses are "bad cops." If they hang around, arms crossed, toes tapping on the shag rug, your resolve will weaken like nobody's business. Tip: Say you sure have a hankering for a nice big batch of onion rings, and could the spouse take the baby into the kitchen and deep-fry up a batch for you.

Never show fear. If you waffle at the prospect of cracking open a tape drive with a screwdriver, or tapping it with a balpeen hammer, or poking it with a barbecue fork, what good are you to your friend in need? You wouldn't want to wake up in the middle of open heart surgery and see your doctor holding your heart in his hand and with an insecure expression up above the surgical mask, where his eyebrows are, would you?

Don't ask permission -- ask forgiveness. The moment friends ask your advice, they empower you to do what you think best. No hand-holding, no charts and graphs, no bibliography and no cost-benefit analysis. Just dive in there and start yanking.

Put humor in your toolkit. Keep up a lively patter while disassembling. Let your friend be in charge of the things you pull out, like the little screws. When it's time to put them back in, tell him it's very vital that he hand them back to you in the order you gave them to him. The look on his face is worth the price of admission.

Accentuate the positive. You wouldn't be knee-deep in your friend's transistors if something wasn't wrong somewhere. Chances are something will need replacing, and some of these things cost money. If you squeeze a little hard on the chip extractor, and the chip caves in, quickly allay your friend's needless worry. These computer parts aren't designed to last forever, after all. Tip: Think of peripherals as fan belts; early and frequent replacement is the surest way to guarantee a long and purposeful life for your computer.

When you screw up, make like it's a breakthrough in human knowledge. No one expects perfection, just a good honest effort. When you fall measurably short of perfection, take solace in lessons learned. I can't begin to convey how comforting it has been to hear me say things like, "You know, the manufacturer of these diskettes should put warnings on the sleeves about the dangers of microwave ovens," or "PC Magazine pays $50 and a T-shirt for stories like this one about what happens when you hook up a laptop to a car battery."

Expect no reward for all your kindnesses. How typical it is of human nature: you come to your friends' assistance, you open their computers, and in the course of your examination you accidentally tip a beaker of boysenberry pancake syrup over the keyboard. Hey, it happens. But do your friends rush in, as real friends are supposed to, to reassure you that it's all right? No, they turn on you like vicious rabid dogs.

Start deflecting blame early. Ideally, before the first plume of smoke appears. Say things like, "Man, don't you ever vacuum in here?" Or, "Looks like a classic case of penny-wise and dollar foolish." Or, "Are you sure you read the installation manual from cover to cover before booting up?" Take a tip from the major players: It's always the end-user's fault.