Reminds me of this classic Windows 98 (I believe) login screen bypass. https://i.imgur.com/rG0p0b2.gif
The error dialog in the gif when Cancel is pressed does say "You cannot use Windows unless your login name is validated by the network."
Just messed around until I found that accidentally, and I was able to run commands.
It would have been around 18 years ago, something like that.
If you want to prevent this you need full disk encryption
To protect from that threat you need secure boot which verifies checksums from BIOS to kernel.
Secure boot, and temper-evident device seals, form the outline of a solution. As far as I know though, these are still far from foolproof. Really I would say defending from an evil maid attack is still an open problem.
Something very similar holds for theft of devices that are still on.
On windows though, we discovered that if you use the save or open dialogs you can just browse wherever, right click, and run the exe.
It sounds like that was a bit before your time, security was even more laughable then. Oddly, the network was set up perfectly, at least according to the standards of the time.
Fun times!
Let us assume one can’t easily modify the filesystem or special boot options are not available
May be its not the Windows but 90s & early 2000s ... don't know.
On early Windows 10 versions, you were able to re-enable it by stopping the window manager from creating the modern theme resources, I'm not sure if that still works but it leads me to think that they did it for brand reasons. Classic theme is distinctly "old" and they probably wanted to get rid of that conception.
Good times playing Age of Empires and Half Life on school computers over LAN using that!
We played Quake mostly!
I did this exact same trick (passed network login though) to get out of it! Although, mine was to go to c:\windows, type . then right click explorer.exe and click open!
That, or get lucky by clicking around a lot.
I was a kid then. Kids these days are finding these sorts of "exploits" in phones and whatnot all the time.