> It's kind of amazing to look at the archaeology of how Windows works because it's the accumulation of cruft over literally decades. For example every exe file first begins with a DOS program that prints "This program cannot be run in DOS mode" followed by more headers that are then parsed by Windows.

That was not the case with defrag or regedit (or was it another register editor tool...). I remember using it without windows to backup and restore the register. This allowed me use windows as I wished and if it simply became slower because of the register, I could simply restore it.