看到「Why does part of the Windows 98 Setup program look older than the rest? (2020) (retrocomputing.stackexchange.com)」這個，原文是 2020 的討論：「Why does part of the Windows 98 Setup program look older than the rest?」。
問題是 Windows 98 的安裝過程中段可以看出來有 Windows 3.1 介面的感覺，像這樣：
而到了後段又是 Windows 98 的感覺，作者覺得 UI 介面風格不一致的問題...
回答的人則是解釋得很清楚，第一階段是 DOS 階段，會把 Windows 3.1 環境疊出來：
The first, which can run from the setup floppies and/or CD-ROM, uses a DOS program (DOSSETUP.BIN) to set up disk partitions, run various checks etc.:
This phases finishes by copying a minimal version of Windows 3.1 to the target installation drive, in a temporary directory (normally WININST0.400), containing DOSX.EXE, USER.EXE, GDI.EXE, KRNL386.EXE, LZEXPAND.DLL etc. (see MINI.CAB).
第二階段則是 Windows 3.1 環境，把 Windows 98 大多數的東西都複製到硬碟上：
The second uses this minimal Windows 3.1 to run a Windows 3 program, W98SETUP.BIN (specified as the “shell” in SYSTEM.INI):
This starts by copying more files to support all the information-gathering during setup, and various other niceties including the 3D look shown in your screenshot (the contents of the PRECOPY CABs); it ends by copying most of Windows 98, setting the system up so that it will boot Windows 98 from the target drive, and rebooting.
第三階段則是 Windows 98 環境，執行後續的設定程式：
The third runs after the first boot into Windows 98, from Windows 98:
而且也提到了當年可以升級作業系統的情況 (雖然我自己偏好重裝)：
It is also possible to initiate the setup process from any of the above environments, which is how Windows 98 handles upgrades (from MS-DOS, or Windows 3, or Windows 95).
是個解釋遺跡的現場 XDDD