Thanks to everyone who played along in yesterday’s troubleshooting quiz.

The consensus answer was correct: My video card had come loose and needed reseating in its slot.

Clue number 1 was the complete absence of display on the screen. That could have meant that the monitor(s) had become unplugged, but the power lights were still on, so that clearly wasn’t it. Any kind of software failure or a corrupted hard disk would have allowed the Power-On Self Test routine to appear on screen before failing.

It had been a warm day, so I considered the possibility that the machine had overheated. But if that were the case I would have known it, because the fans would have been working overtime right before the failure. And the fact that it didn’t restart even after a proper cooling-down period ruled that out.

Memory errors? Those usually result in visible failures – random crashes and misleading error messages. I wouldn’t expect bad RAM to shut down the whole video subsystem.

That left two options: Motherboard failure (bad) or problem with video card (not so bad). I strongly suspected the video card because of the three beep tones. This is an Intel board, as I pointed out obliquely in the description of the problem. I turned to a handy list of error messages associated with each beep code on this machine. (If you have a different BIOS, visit that page and follow the links in the sidebar.) Three beeps – one long, two short – means a video adapter problem.

I unplugged both monitors, removed the PCI-e video card, visually inspected it to make sure nothing was obviously wrong, and reseated it in its slot. When I turned the computer back on, I had a signal to both displays again. If this step hadn’t worked, the next option would have been to try another video card.

So, how does a card come loose in the first place? Well, this machine has been jostled around a fair amount in the past few months as I’ve swapped out various components (network cards, hard drives, TV tuners) while testing Windows Vista. In all that moving, I never fiddled with the video card. But it obviously had come loose enough (a micron here, a micron there, pretty soon you’re up to half a millimeter) that one slight motion did it in.

Props to Carl, who was first to suggest this solution.

No prizes this time, but next time I’ll give away a book or two and make the challenge a little tougher.

Ah, the joys of hardware!

Last night, as I was reaching the end of the first shift (5:00PM, which is followed by a dinner break and then the second shift – ah, the joys of writing books about beta software), my computer screen suddenly went black. A second earlier, I had a half-dozen apps open, and then … nothing.

After trying in vain to make something reappear on the screen, I pressed the power switch, held it down for five seconds, and waited as the computer restarted. This time I heard, from inside the case, three faint beeps. Nothing appeared on the screen, however. And I mean nothing. No BIOS messages, no Intel logo, no prompts from a storage adapter … nothing.

I took the cover off the computer, powered it on again, and checked inside. Everything looked normal. All fans were working, I could hear chattering noises from each hard drive at startup, and nothing was emitting smoke.

Eventually, I solved the problem. What troubleshooting did I have to do, and what was the solution?

All the information you need is in the post above.

Update: I have two monitors attached to this system. Both went black at precisely the same time, and the power light remained on for each one. So no, the solution wasn’t as simple as plugging in the monitor.

There have been some good comments so far. The correct answer might even be in there already. I’m going to leave comments open for the rest of the day to give working folks (especially those who can’t check this site during the workday) a chance to take a crack at it.

Update #2: This is not the same computer that experienced memory problems a few weeks ago. That was a Dell server. This is a desktop machine that was built by Mwave in August 2005.

OK, here’s the answer.