After having reanimated the old system and after comments of other
persons I would not be inconvenienced if the option went away.
The system indeed did not boot correctly without that option, because
the disks appeared in a wrong order. On the other hand, I was able to
(re)install bootloaders (grub as well as lilo) and after that did not
need the option any more. Unfortunately, after that I was not able to
reproduce the initial situation where the option was needed.
Dirk
--