Ok, so I've got a Windows 95 machine which tells me "Windows has detected a registry configuration error", and prompts me to boot into safemode at the boot menu. The problem is, it won't boot into ...
Someone saw a 30-year-old OS and thought it needed a Linux subsystem.
I think it would depend on the motherboard. Some can make a USB drive appear as an INT 13 device, and I've seen some USB drivers for DOS.