A desktop PC was dead as a doornail. All tests indicated a failed motherboard. Before tossing it, I closely examined the motherboard and noticed that several of the radial lead electrolytic filter capacitors ("caps") had bulging ends. A Google search revealed that indeed this was a problem when this motherboard was built: gas pressure pushed out the ends as the electrolyte "boiled" over time. I bought replacement capacitors and, though I was skeptical that the repair would work because of the tiny traces and solder pads on the motherboard, I replaced the bulging capacitors. To my surprise, the PC came back to life!

Read more about this problem: http://www.badcaps.net/