I’m an elder Millennial, and I remember when we got old enough to use the 386 machines at school. Before that we were using DOS.
Our first home computer was bought second hand and didn’t even have a hard drive, just two 5.25" floppy drives, and also ran DOS. We’d have kids from the entire neighborhood visit to play games on it, because although it was second hand it was also very rare to have one.
I was 12 when Windows 95 came out. All this stuff looks waay newer than that. I’d say this draws the line for old at the older part of Gen Z. Millennials aren’t even on the scale.
I never had to do that, because our computer didn’t have a hard drive. We booted DOS right from the floppy.