
new (or wiped) disk (no MBR/no partitions) -> Bootfix is NOT invoked at first boot, then text mode setup is run -> MBR and partition made, AND formatted AND setup files copied to hard disk -> bootfix is invoked to allow - if needed - to STOP the installing (the procedure is that second boot comes from hard disk, and the bootfix.bin is there because after text mode you should boot from HD, and without it (or changing the BIOS boot order) the install would start again from CD, which is wrong.
With a "normal", "attended" CD the procedure is simple and there are only two possible cases: Looks like I would have to have a bootmanager check if the hdd was still in 'Windows Setup Mode' and bypass the CD in that case and boot CD in all other cases.