He's Dead, Jim
I can count only a handful of times that I've experienced some kind of computer hardware failure. The most recent was a little over a year ago when the power supply in the desktop blew out unexpectedly. This morning, I got the rare "pleasure" of experiencing it again when I found that the desktop refused to power on. It was obviously still getting power because some of the lights in the back were still on. I tried everything I could think of, even swapping the power supply with a spare that was sitting around. No dice. My best guess is that the motherboard, after 5 long years of heavy usage, finally decided to give up.
I'd been putting off upgrading for a really long time. In the last several years, the entire PC market has gone through a big shift and compatibility has died with it. Upgrading is no mere swap of your core components; it's now a matter of building an entirely new system from scratch. In addition to the normal motherboard, memory and processor swap, I was looking at a new case and video card. Old IDE hard drives and CD burners? Gotta toss 'em; IDE is out, SATA is in. After all is said and done, a new baseline system with decent upgrade capacity is over $600, even when sticking to lower-end components.
I'd been hoping that the desktop would give us at least a year or two before biting the dust. I always get nervous once PCs pass the magical 3 year mark. After that, you're living on borrowed time. Some PCs (like the old clunkers in the basement) are on year 10 of service, but there has been a marked decline in PC quality as component reach commodity pricing. Now that electronics are considered disposably cheap, manufacturing anything that lasts much past the warranty is a mere afterthought. Here's to hoping that the new desktop, whenever it gets built, has better luck.