When called to repair a computer system, most good service people (and all of the bad ones) know how important it is to get your hand on some part of the system as soon as you get there. Then, you have to keep your hand on that or another part, preferably important looking, all the time you're wondering what on earth you're going to do. The reason for this is obvious: when the system suddenly starts working of its own accord, it's essential that you be able to say: "Yes, I thought that'd fix it."
Good diagnosis is essential, and the first thing you have to do is spot the difference between non-functioning and malfunctioning. After all, a totally dead system often means the cleaner left the plug out after vacuuming last night. Another good one is the dead monitor where the user has never had to turn it on or off because either it's powered by the PC or it's green, and powers down automatically. I hear it's amazing how many support calls find the monitor's front panel power switch subtly set to the "off" position.
Then there's the computer or terminal that people move to their new office (minus the network connection) and wonder why it barely gets beyond a blank screen. Or what about the manager who used to keep two PC systems on his desk - one connected to the company's accounting system and the other for personal productivity. He called for support at least once a week to complain that either his keyboard or mouse had stopped working. "Use the other one!" they'd yell down the phone. "You're using the wrong one." And before you ask, no, he refused to let anyone set up one PC for both functions, and even refused a switchbox to halve the number of monitors, keyboards and mice on his desk.
Once you've eliminated all the obvious likelihoods, it's time to ask the owner of the system to go into the kitchen and boil some water. Once they're safely out of ear- and eyeshot, you subtly lift the system a few centimetres off the desk and drop it. Known as "percussive maintenance", this works in 84.876 per cent of all cases.
Well, it works often enough to make it worth a try. Simultaneously, you reseat all the expansion cards and SIMMs, you free the hard disk suffering from "sticktion", you knock that loose connection in the monitor back into place, and you show the computer who's boss, all in one quick movement.
If the system is still non-functioning at this point, the user obviously needs to upgrade to a Pentium II machine.