I needed to reboot so I did a normal shutdown. No big deal.
It shutdown and started to come back up but never got past the POST. So I rebooted again and got the same thing... I opened it up to see what was going on and noticed there was a lot of dust collected on the CPU cooling fan and fins. It obviously needed to be cleaned so I go my lovely wet-dry vacuum out and reversed it so it would blow instead of suck. (If any of the ladies don't know why I called it "lovely" its because you are female don't get the "manly rush" men experience when operating a powerful piece of equipment. *Grunt* *Grunt* *Grunt* )
Anyway... I started blowing all of the dust out, which caused the CPU fan to spin faster and faster until it started to sound like a siren. "Hot damn! I've got a great wet-dry vac", I was thinking to myself.
Then it happened... a bright flash of light accompanied by a very loud BANG!!!
It sounded like a capacitor exploded, so I looked around the motherboard to find the remains of an exploded capacitor, but I didn't see it. It must have been in the power supply.
It's obvious that my #1 mistake was leaving the computer on while I blew the dust out of it. I suspect I had the fan spinning so quickly that it created a large amount of current going backwards. Basically it was acting like a little electric generator, only it was pushing the electricity against the power supply instead of with the power supply. The poor thing could only take so much before it blew.