Q:

While installing software today, I noticed that the power source wasn’t plugged all the way into the video card, so I pushed it in more tightly, and bam: The computer suddenly shut off, and it won’t turn back on.

Do you think I’ve fried the computer’s motherboard or its power supply?

A: First, a rap on the knuckles: Always unplug your computer before working inside your PC. Even if you’re just tightening a connector, turn off and unplug your computer first.

Now, back to your question. When troubleshooting a potential power supply problem, let your ears be your guide, by listening for these things:When you turn on your PC, do you hear the power supply’s fan whir into action? Even the quietest fan can be heard when you place your ear next to the round vent on the back of your computer.

If you don’t hear a spinning fan, then you’ve killed the power supply. That’s a fairly inexpensive and easy-to-install repair.

But if the fan still spins, the power supply is probably still alive, so your motherboard might be dead. Motherboards cost more than a power supply.

There’s another scenario: If you hear the fan and you hear your hard drive clicking and whirring as it loads an operating system, then you might have killed something else: the video card.

To further isolate the problem, turn to your stash of old parts and begin swapping the suspect parts with old ones you know to be good. That makes it easy to find the bad part, and lets you avoid a trip to the repair shop.

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How do I get rid of this message?

A: You’re seeing yet another annoying Windows Vista feature. When you try to run some programs, Vista’s User Account Control (UAC) normally steps in, asking if you’re sure you want to run the program. (UAC is a safety mechanism that I cover in Windows Vista For Dummies.)

The message you’re now seeing means that one of your recently installed programs needs your click of approval. However, that particular program is trying to run as soon as you log onto your account. Since UAC doesn’t have time to step in, Windows simply stops the program from running, and sends you the message.

To stop the message, follow these steps:

1. Click the “Blocked startup programs” icon on the taskbar, and point to the “Run blocked program menu” list. There, in the figure below, you’ll see the programs Vista has blocked from starting.

2. If you want to run the blocked program, click its name. Type your password, if prompted, or click Continue, and the program will begin running. (Unfortunately, you must repeat these steps every time you log onto your account.)

3. If you don’t want to run the blocked program, or you’re not sure what to do, choose “Show or remove blocked startup programs.” Windows Defender appears, listing every program that starts automatically.

4. Click the name of the program you don’t want to run, and click the Disable button. (If you change your mind, repeat these steps, and click the Enable button.)

This message often appears in Vista after you install antivirus or other security programs. Those types of programs both require your approval to run, and they want to run as soon as you log onto your account. If you’re tired of seeing the message, check with the program’s manufacturer to see if they have an updated version that doesn’t trigger the message.

Microsoft’s support site offers more technical information about the error message.

Anthrax virus, courtesy of the Centers for Disease Control and Prevention

Q: I was scanning my laptop for potential threats, and the scan results stated there was a “threat agent” on my laptop. I know what a threat is, but what’s a threat agent. Is there a difference?

A: The word “threat” usually stands for a category of things that pose a potential danger. Viruses, worms, and other types of malware, for example, are threats. A “threat agent,” by contrast, is a specific threat, or a specific type of virus, worm, or other malware. For example, the Blaster Worm is a threat agent.

So, it sounds like your laptop has picked up something nasty, and should be disinfected. I like Microsoft’s free antivirus program.