Little problem migrating a server

Hi all !

This problem isn't tao-specific, but I'd like some help...

I have a machine here (an old pentium-2 with about 128 megs of ram), the
power supply of that machine, that is somewhat critical, was dying.

So we bought a new machine:

Intel motherboard D865PERL (ICH5 based), with 200 gig serial ata disk.

The driver to be used with this controler is ata_piix and is included with
tao. So to make the migration, I booted the first install cd into rescue,
patritionned, make fs' and mounted the new disk, I then copied all from the
old hd (plan p-ata ide) to the new one.

I also manually installed grub into the boot sector, modified device.map,
grub.conf, fstab, etc...

While in this mode, I ran kudzu, so it detected new hw, and unconfigure old 
one.

If I boot the system normally, I see grub, and then the kernel panic with :

failed to exec /sbin/modprobe -s -k block-major-8, errorno = 2
VFS:cannot open root device "801" or 08:01
kernel panic:VFS:unable to mount root fs on 08:01

Or somthing like that...

Now, I am able to boot the system with the install cd in rescue mode, and
then chroot /mnt/sysimage, and then start the critical services manually
(network, named and samba...)

I've done some google on this, I found some reference that some linux won't
support more than 4 ide devices, thus I had to set my bios into "legacy"
mode with sata p0/p1 - pata primary only enabled; didn't help.


modules.conf :
--------------
alias scsi_hostadapter ata_piix
alias usb-controller usb-uhci
alias ieee1394-controller ohci1394
alias eth0 e100
alias usb-controller1 ehci-hcd

grub.conf :
-----------
default=0
timeout=8
title Tao Linux (2.4.21-27.0.1.TL)
        root (hd0,0)
        kernel /boot/vmlinuz-2.4.21-27.0.1.TL ro root=/dev/sda1
        initrd /boot/initrd-2.4.21-27.0.1.TL.img

device.map :
------------
(fd0)     /dev/fd0
(hd0)     /dev/sda

fstab :
----------
/dev/sda1               /                       ext3    defaults        1 1
/dev/sda3               /usr                    ext3    defaults        1 2
/dev/sda5               /var                    ext3    defaults        1 2
/dev/sda6               /stuff                  ext3    defaults        1 2
/dev/sda2               swap                    swap    defaults        0 0
none                    /dev/pts                devpts  gid=5,mode=620  0 0
none                    /proc                   proc    defaults        0 0
none                    /dev/shm                tmpfs   defaults        0 0
/dev/fd0                /mnt/floppy             auto noauto,owner,kudzu 0 0
/dev/cdrom              /mnt/cdrom    udf,iso9660 noauto,owner,kudzu,ro 0 0


Any hints on what I missed ?