Windows XP required a minimum of 64 MB of memory. The installer must not only fit in that space, it must be able to run at the same time. Not an impossibility,

Windows XP required a minimum of 64 MB of memory. The installer must not only fit in that space, it must be able to run at the same time. Not an impossibility, but a much taller order than running the same/a previous version of the OS directly off the disk. I have definitely used OS installers that allowed/required CD swaps, though. Maybe Ubuntu at one point? Now that's a slick setup process. Opening Firefox to read the orange site while your OS installs on the same computer is a great trick.