Thanks, it looks impressive and I will have in mind when I install a new system.
As for my existing problem, somehow my /boot partition, which was there just to boot, doesnt seam to find the LVM partition, even though I use the same menu.lst which I now use to multiboot, but which is in the the root directory of the latest linux OS.

I found a temporary solution!
I can boot into my opensuse.

I put the MBR in /sda5 and I am able to boot opensuse on the LVM in /sda4 from there.
However, originally I was booting from a /boot partition inside my LVM, inside /dev/system/root, and the MBR is not found there anymore.
(I was confused, my /boot partition was useless, the kernel there was not anymore valid.)

typing from /sda3 or /sda5,
grub>find /boot/grub/stage1
did not show me an entry in the LVM, so I assumed it was not used.

the same thing now in my opensuse only shows me the opensuse file.
It seams to be isolated.

I expect some trouble in the future, but so far its fine.
Too bad for the lost afternoon.

fp

I need to correct a typo above:

In my menu.lst file I actually have

root (hd0,2)
kernel /boot/vmlinuz root=/dev/system/root
resume=/dev/sustem/swap ...

[instead of root (hd0,3), since the kernel is actually on the /boot partition, as I understand it should be]