Every network technician has experienced the following situation:

User: "Hello. My computer isn't working."

Tech: "What's the problem?"

User: "I can't connect to the Internet."

Tech: "Have you checked to make sure the cable is securely plugged in to both the wall and the computer?"

User: "Yes, that was the first thing I checked."

Tech: "Have you rebooted?"

User: "I did that right before I called you. It's always the first thing you have me try."

Tech: "Has anything changed on your system recently?"

User: "No."

Tech: "Nothing?"

User: "No, I haven't changed anything."

Tech: "You're certain?"

User: "Yes, I'm certain! Nothing has changed since the last time you were here."

Tech: "What about this program--UberSpy Deluxe? That's not part of our standard install."

User: "Oh--my son put that on yesterday afternoon. But it's just a game or something. Do you think it could be causing the problem?"

This is a frustrating scenario, for both the user and the technician.

If multiple people have access to the computer in question, the user may not know when someone else changes his settings. He may have changed the configuration himself, but inadvertently, so that he honestly doesn't know a change has been made. Or the change may appear so inconsequential that it slips his mind when talking to the technician.

The technician knows from hard experience, however, that--generally speaking--computers do not just stop working on their own. If the cables are functioning properly, and if rebooting does not fix the problem, then the odds are good that something, somewhere, has been changed. More than that--someone made the change. If that person can tell the technician what happened, the technician can probably resolve the issue.

In a way, this is an extension of the software configuration discussion from last week's topic, "The Simplest Things Break First." It is very easy for a configuration setting to get changed--but it is not always easy to identify that change after the fact.

Even though this topic is called "It's Probably Someone's Fault," in reality, a technician is usually not looking for someone to blame when he asks what has changed. He is simply trying to identify the cause of the problem. It helps (a lot!) when users consider the question carefully, and tell the technician about anything they can think of--even if it seems unimportant.

Should you find yourself in a situation where you must act as your own network technician, identifying recent changes is even more important. A professional technician can always fall back on his experience and training, in an effort to solve the problem through trial and error. If you don't have a similar background, determining what has changed may be your only hope of getting back to work quickly.

Ask yourself, and everyone you work with, to think long and hard about what has been done to the computers over the past two days. Special attention should be given to any software downloaded and installed, and to any settings that have been adjusted, or even looked at. Everything, however, should be considered--no matter how small.

Make a list of all the changes (or potential changes) you can think of--arranged in the order of when the changes were made.

Then, go through the list one-by-one, starting with the most recent changes first. Reverse each change, to see if that resolves your problem. Uninstall any software that may have been installed. Return any altered settings to their previous values. Don't worry, for the time being, about whether or not you need the change. Right now, you are just testing.

If this troubleshooting process works, and the problem you are trying to resolve disappears after you reverse one or more changes, then you will be faced with a decision: do without the change--perhaps by finding some other approach that will achieve the same goal--or live with the problem caused by the change. Of course, you may only have to put up with this choice until your network technician arrives. In the meantime, you will at least understand the source of your trouble, and how best to work around it.