The tables did turn on that more recently, when he was having trouble with his computer (an ancient-by-today's-standards Dell Optiplex running Windows XP); his power supply died, so I bought him a new one, but after he installed it he wasn't able to boot into Windows anymore. I figured maybe whatever blew the PSU also blew the hard drive (I've seen that happen before), so next time I was at his place he handed me the tower to take home and diagnose/rebuild.

As he's handing it to me, it dawns on me, "Well wait just a second..."

On the spot, I popped open the case, took a quick look at the hard drive, plugged in the Molex cable, put the cover back on, and handed it right back to him.

Hearing the words "Alright fucker, we're even" made my week.