Hadn’t seen Paul cover it, but for 2004, Microsoft no-longer allow any OEM to pre-install a 32-bit version of Windows 10 2004:
(You can still use 32-bit Windows 10 on a personal basis, and businesses can still install it; it only affects pre-built laptops/desktops/tablets you’d buy online or in a store)
I’d be curious to know how-many PCs actually do run 32-bit versions of Windows 10: the Steam user-survey for April 2020 says 64-bit versions of Windows 7, 8 and 10 combined make-up 94.4% of all their user-base, and 32-bit Windows 7 and 10 make-up around 0.6%.
I’d also be curious to know for what reasons you’d still use 32-bit Windows 10 on a new PC: sure, sure, “16-bit app support” or “32-bit driver support”, but in a business setting, why would you not just keep an older version of Windows on that PC, and segregate it from the rest of the network / Internet? Likewise I’m sure most retro-gamers won’t bother frustratingly trying to get Windows 9.x games to run on 32-bit Windows 10 (endlessly scouring forums to find what DLL files they need to put into the folder, and other hacks) when they could just run Windows XP, 2000 or 98SE and be-done. (And DOSBox will meet most of your MS-DOS gaming needs, and installs on 64-bit Windows 10).
So… for what specific reason would one absolutely have to still use 32-bit Windows 10 for thesedays, that an older version of Windows (isolated from threats) wouldn’t work for?