My dude, the first operating system I bought was MS-DOS 6.22. I went miles and miles out of my way, because there was a community college in my area that was (possibly crookedly) selling it to people with the student discount, even if they weren’t students. I have forgotten the exact details, because of all the intervening years.

Then I got Windows 3.1 pre-installed on several machines, then bought the Windows 95 upgrade package, then Windows 98, then XP, then a machine that already had ME, then one that already had Vista, then I bought 7, then I bought 10. They were all annoyingly expensive.