I love that some of these old UIs are still present in current Windows 11 22H2. I was surprised "control userpasswords2" still exists.

With certain programs (in this case Paint Shop Pro 5), you can get Windows 11 to render Windows Aero.[1]

[1]: https://cdn.discordapp.com/attachments/747297210613498216/10...

That's excellent. I wonder how deeply the UI elements go. Like can I produce a UI from Windows 3 or 2000 on Windows 11 if I make the right Win32 calls? Is the classic theme really gone, or just aggressively hidden? The new Windows 11 taskbar is definitely new code and doesn't behave like the old one, so I imagine you can't have a true classic taskbar on 11.

That's the officially deprecated for decades "Multiple Document Interface". Any app still using it will render that on modern versions of Windows.

The open source Windows all I maintain still uses this paradigm, and there's not really a good migration path to anything else, and Microsoft refuses to fix the chrome.

That's not "real" Aero (as in the GPU accelerated effects that came with Vista); it looks like the "Windows Basic" theme in Windows 7.

Aero looks like this:

https://upload.wikimedia.org/wikipedia/en/d/df/Aero_Example....

Yes, it's Windows Aero minus most of the 3D accelerated special effects. It was also used on low performance systems or if you RDP'd in to save bandwidth.