What's the one thing you never want to see your computer do?
Well, opinions vary on this, but the emission of smoke is definitely high on most people's lists.
I just moved into a new apartment, and I was setting up my desktop computer here for the first time (not the Powerbook, fortunately). I plugged everything in, connected all of the cables, then turned on the UPS. I hadn't turned on the computer yet, but I started to smell something vaguely familiar. I thought, "I know that smell, what is it again?... OH NO!" When I went to pull the cord out of the computer's power supply, I was greeted by a nice little puff of blue-gray smoke.
Yes, that was the smell of a melting capacitor. I sat there in shock for a minute, trying to decide what to do next. Against my better judgment, I plugged it back in. No smoke. I turned it on.
It got to the XP login screen, and I could move the mouse. That's all I needed. I unplugged it, tore open the case, and pulled out the power supply. I opened it (don't do this, it's dangerous) and looked around for the dead capacitor. The smell was definitely strong, which confirmed that it was indeed the power supply and not another component with capacitors (like... most of them). But I didn't see anything obviously burnt.
An exploding power supply is generally not a good testimonial to its manufacturer, but here, I have to make an exception. This was from POWMAX, a generic PSU manufacturer, and it came in a generic case that I bought in 2000. It was one of the cheapest power supplies available. I had previously opened it up (you're not supposed to do that) to replace the fan with a quieter one (you're really not supposed to do that) and I had to splice the wires on the non-standard fan connector (you're definitely not supposed to do that). It was rated at 300W, and I used it at almost full capacity for the majority of its life. It was rarely turned off. Before I bought this UPS in 2002, it was plugged into the cheapest surge protectors and fed dirty, unstable power. It's been moved more times than most college students. And I have a homemade fan controller that uses the +5V instead of ground with the +12V to get a 7V fan current (you're absolutely never supposed to do that), powering all of the fans through badly-spliced RCA audio cables instead of Molex connectors because they're easier to plug and unplug (my computer really should have burned down the building). To complete this wonderful set of conditions, I haven't blown the dust out of my computer for an entire year, and it has built up to such a degree that I'm amazed the fans still move.
I horribly abused this power supply, and when part of it melted, it continued to work. Most surprising of all, I don't think it killed any of my components. It may have damaged the RAM or hard drives slightly, but I got to the XP login screen - that's a pretty good indication that the components are in pretty good shape. This is a much better result than the last time I smelled a burning capacitor, when the power supply in Mark's Quantex computer died and killed almost every component in the system.