11-12, 2008. I've a family friend who teaches various computer science lectures at college. He invited me down and I ended up spending a week learning about various thnigs just about in my grasp along with taking apart computers and putting them back together, everything from 486es to P4s along with tearing down broken computers and salvaging parts into something working. By the end of the week I had probably built something in the order of 50 computers.
I made a computer for myself about age 14. It was easy, I'd done enough already and this time I could pick which parts and know they worked. However with it built it quickly became apparent where my knowledge lacked. I had 1 case fan and a cheap overburdened PSU. Every computer I had built up to that point was either old enough that power and temperature wasn't an issue or for the P4s new and I was given the full set of components. My computer ran bordering on the thermal shutoff, would need the side removed and a desk fan to keep it gaming in the summer, and was built on an old socket after it became outdated, and ultimately I'm incredibly surprised it ran for a year let alone 6 (and still going).
My current computer was built around 2012 age 16 and uses everything I screwed up with the old system. I went AMD as Intel seem to like swapping sockets and motherboards, I prized low temperatures and low noise possibly a little too much, and I used quality components. I've since built a few friends computers and that design goal hasn't changed at all. One wanted flashy lights and cheap components and ended up swapping out all of that for quality and low noise himself after a while.