Turbolinux 6, which was the first Linux distro I tried and which I never successfully installed because I was a high-school kid and had no idea what I was doing.

(Why Turbolinux and not some other distro? Because it's the one I found a physical, boxed copy of. I can't remember if I bought it at a store or somebody gave it to me at a Ham Fest -- more likely the latter -- but I definitely didn't download it.)