Back in 2008 when I was 10, (and yes my vintage computer enthusiasm really goes that far back,) I had a PowerBook G3 Pismo that my dad had bought off eBay, that I played with all the time. I was a curious kid who was always asking questions and taking things apart to figure out how they work, so naturally I found dad's Philips screwdriver (which they had to hide due to these occurences) and dug into the Powerbook.
I unscrewed every screw I could find, and in the process I took off the CPU heatsink, and threw it away because I didn't know what it was. Kid logic. I plugged it in to the outlet then and while I was at school, the PowerBook started smoking and our house's smoke alarm went off. Immediately it was unplugged and hidden away, when I asked my dad what happened he told me he threw the laptop away because it caught on fire. I found it a few years later sitting deep in one of our closets, I salvaged everything I could from it (keyboard, RAM, hard drive, battery and DVD drive) and threw the rest away.
And then there was the time, the same year I think, I wiped the hard drive on the family computer attempting to install Ubuntu Linux. I have enough stories of stupid things I did as a kid to fill an entire book.
Pluto, the maxed out Dell Dimension 4100: Pentium III 1400S | 256MB | GeForce4 Ti4200 + Voodoo4 4500 | SB Live! 5.1
Charon, the DOS and early Windows time machine: K6-III+ 600 | 256MB | TNT2 Ultra + Voodoo3 2000 | Audician 32 Plus