So just explain siince the beginning .. I had install knoppix 3.1 on my hd .. working well no problem with my lilo (that change some option and re run without any kind of pb..)
But following a power pb (even witth reiserfs) I had to restore my partition table with gpart (because even with the live cd I couldn't access at any type of partition even ntfs or fat !!) so this big problem solve just reboot and I see that lilo wasn't any more here ..
(say no pb nothing very hard now ..!)

So i boot with the live cd
and write as usual
#sudo su
#mount /dev/hda3 /mnt/hda3 {my / partition in reiserfs}
#chroot /mnt/hda3
#lilo-v

But here i had this error

bash-2.05b# lilo -v
LILO version 22.4.1, Copyright (C) 1992-1998 Werner Almesberger
Development beyond version 21 Copyright (C) 1999-2002 John Coffman
Released 27-Jan-2003 and compiled at 09:45:24 on Feb 27 2003.

Reading boot sector from /dev/hda
Fatal: open /dev/hda: Permission denied

so I just check if my bios was protecting my mbr against some virus
(I have win so can be useful to activated sometimes) but wasn't activat..
so i look after some doc on the man page and see the
install-mbr /dev/hda
we look like to work
(I've seen the "mbr" print on my screen after it and always boot on win .. ;-( )
so I just try again lilo and nothing different .. Grrrr

so here a part of my lilo.conf
################################
vga=791
lba32
boot=/dev/hda
root=/dev/hda3
install=/boot/boot-menu.b
map=/boot/map
prompt
timeout=150

append="hda=scsi hdb=scsi hdc=scsi hdd=scsi hde=scsi hdf=scsi hdg=scsi hdh=scsi nomce"

default=Linux
image=/boot/vmlinuz-2.4.20-xfs
label=Linux
initrd=/boot/initrd.gz
read-only

image=/vmlinuz.old
label=LinuxOLD
read-only
optional
other=/dev/hda1
label="WinXP"


all point of view or comment .. are welcome ..