IBM Thinkpad X24 - geometry 240 heads

(UPDATED) now i dont care about the 240 thing anymore,
i'm happily using the configuration of 255 in both FreeBSD and Linux,
and i've backed up the 'F11' rescue partition and then deleted it..

In freebsd installation: answer "No" when asked if to use the 'safe setting' of 16 heads, answer "OK" (temperately) when the next screen says a new geometry was calculated for your drive. But in the next screen, where we can partition the freebsd slice, press (G)eometry to change to the correct setting (CHS=xxx/240/63)

In linux installation: at the "boot: " prompt, enter "linux hda=xxx,240,63".

how do i know the correct cylinder value?
(1) the brutal "F11" method when you create a partition out of wrong geometry,
(2) boot from some linux installation cd: (to be tested)
boot: linux rescue
chroot /mnt/sysimage
fdisk -l /dev/hda
Disk /dev/hda: 40.0 GB, 40007761920 bytes
240 heads, 63 sectors/track, 5168 cylinders
Units = cylinders of 15120 * 512 = 7741440 bytes