In the days when Windows was easier to crack, it was not uncommon to find very small, specialised ISOs of "miniature windows" designed specifically for running a certain task -- typically some form of data-recovery app, system repair/maintenance or similar -- and they would fit on a single CD-R, have almost no system requirements, and, if I recall successfully, be bloody useful to my school's computer administrators…
For repair/maintenance, there is WinPE (and now, live USB boot)