I was late getting into computers, and back in '98 just got my first Windows PC. I struggled, but eventually figured out how to get MAME installed and loaded up a long forgotten arcade game I used to play as a kid at my local corner store.
It's hard to describe the sense of wonder I felt when when the ROM check sequence flashed to the title / insert credits screen and I knew it worked. It might sound silly, but few moments in my life have been so eye opening. It was definitely a key factor in me starting my path to becoming a developer.