I could say I begun by the Ti-57, then Sharp PC-1251 and Canon X-07... But it's not really interesting, if you ask me.
After that, I used Windows and still use it as main OS.
Nevertheless, there is a fact: I left linux and I think I'll never come to this OS again. Not because it's bad (I think just the opposite), but one day, back in time, I discovered PC-BSD and I felt in love. When time has come to change for TrueOS or Ghost BSD, I was very disappointed for plenty things.
Then, I came to the source: FreeBSD. It's very amusing to learn how it works, it recalls me the first linux times (slackware was just amazing). Since, I discarded all FreeBSD based distributions.