With searching in Google and trying to run several official unmodified verions of Notepad++ in virtual machines. Notepad++ come with several plugins enabled, which may stop working before Notepad++ version. Please attention that, the installed version of Internet Explorer may affect other software, which I did not test. The following is what I get.
For Windows 95, refer to these links:
http://www.win3x.org/win3board/viewtopic.php?t=17221https://notepad-plus-plus.narkive.com/6lktixGR/notepad-plus-help-notepad-v4-0-does-not-work-on-win95
I've confirmed that Notepad++ 3.9 runs on Windows 95 RTM/OSR 2.5, and Notepad++ 4.0.1 doesn't (4.0 not found, but I think there's only minor changes). So Notepad++ 3.9 is the latest version for Windows 95.
For Windows NT 4.0, nothing found when searching.
I've confirmed that Notepad++ 4.6 runs on Windows NT 4.0 SP6, and Notepad++ 4.7.1/4.7.2/4.7.3 runs with error of plugin, and Notepad++ 4.7.5 doesn't work. So Notpad++ 4.7.3 is the latest for Windows NT 4 with plugins disabled.
For Windows 98/ME, refer to these links:
http://web.archive.org/web/20110709191226/http://notepad-plus-plus.org/news/notepad-5.9.1-release-is-available.htmlhttps://msfn.org/board/topic/105936-last-versions-of-software-for-windows-98se/page/68/#comment-1176861
I've confirmed that Notepad++ 5.9.6.2 (ANSI) runs Windows 98 SE/ME, and Notepad++ 5.9.8/6.0 (ANSI) runs with error of plugin, and Notepad++ 6.1 doesn't work because no ANSI version available. So Notepad++ 6.0 (ANSI) is the latest for Windows 98/ME with plugins disabled.
For Windows 2000, I've confirmed that Notepad++ 6.5 runs on Windows 2000 SP4, and Notepad++ 6.6 with default plugins runs with error, and Notepad++ 6.7 doesn't work. So Notepad++ 6.6.9 is the latest for Windows 2000 with plugins disabled.
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