Hi all, I have a serious problem here: I've had to reinstall win xp (I know I know...) on a previously perfectly working dual boot configuration... I knew the win xp reinstallation would overwrite the bootloader, but I had a good Grub reinstallation procedure: from the Debian install cd, run rescue (or rescuegui), select "Grub reinstallation". Which I did; and actually, I got my Grub back, with splash and stuff. The problem is that Grub looks for root=/dev/sda6, as it should be, but for some reasons, root ended up on /dev/sda5... look:
from /grub/menu.lst
this is fdisk -l
and /etc/fstab
if I compare /etc/fstab and fdisk -l, root is on /dev/sda6 (as it has always be) fdisk -l shows a Linux swap filesystem... If I dynamically change option in grub switching root=/dev/sda6 to root=/dev/sda5, then the OS boots... but it fails of course on loading /swap, /home, expecting it to be /dev/sda8... which it can't find... It's just as if the filesystem table had been all messed up. All partitions mentioned in /fstab do exist : I can "cd /" in them. Other clue : I tryed to see what a partitioning tool would say... Gparted sees the hard drive as empty... no filesystem at all... so does the install cd tools... but f... windows, when booted, perfectly sees all the partitions with its disk manager.... And finally, there's smthing weird shown from fdisk -l:/dev/sda4 starts at the 5863rd blocks, but it should be /dev/sda5 if I look at the starting and ending blocks of each... I don't know if it's related or not.
Is it a matter of mbr ? boot loader ? Please... if somebody had the beginning of an idea... I've already apt-get remove Grub, to then apt-get intall it, with no change. Should I erase the mbr (fdisk/mbr, is it ?)and then reinstall Grub ?
ps : grub-install --recheck /dev/sda didn't solve anything

just change /boot/grub/menu.lst and /etc/fstab to make /dev/sda5 the "/" partition

hun hun I thought about that, but it couldn't be that simple, since all the other partitions are messed up as well: /swap and /home have moved too... I could re-write fstab, according to this too, but it wouldn't be an elegant hack.... there's gotta be a way to fix the partition table

Yeeeeeeeesss !! Using testdisk from Gparted, I fixed up the partition table, which is just right now !!! aleluya... thanx silvagroup. Buuut.... Grub just died in the operation : at boot, "grub loading error 15". I guess I have to reinstall it... What is the best way: should I boot from a live cd, chroot in / and apt-get install it ?

I think you only need to do
grub-install

For this, you will need to have chrooted but before this make sure you link your /chroot/dev to the real /dev
There are probably ways to pass option to grub-install to not do the chroot but I can't remember