How do you recover from formating your partition with grub?

Question

I had my laptop's HDD separated in 3 partitions:

1. NTFS - Win XP install (primary)
2. NTFS - common space (extended)
3. ext4 - Ubuntu 10.10 (extended)

Running out of space, I deleted my 2^nd partition, and formated it to ext4, planning to merge it to my 3^rd partition.
The problem is that after restart I realized that grub was installed on partition #2.

Using grub (GNU GRUB 0.97) an Ubuntu 11.04 live CD, I tried:

grub> root (hd0,4)

grub> setup (hd0,4)
 Checking if "/boot/grub/stage1" exists... no
 Checking if "/grub/stage1" exists... no

Error 15: File not found

grub> 

Also, for setup (hd0) I get the same result.

Right now I have:

1. /dev/sda1 aka (hd0,0) - Win XP (NTFS)
2. /dev/sda7 aka (hd0,6) - the free space (ext4)
3. /dev/sda5 aka (hd0,4) - my previous install of Ubuntu (ext4)

How can I repair it?

Answer 1

This page documents installing GRUB from the live CD:

http://help.ubuntu.com/community/Grub2#METHOD%203%20-%20CHROOT

Answer 2

Ubuntu has moved to grub2 since 9.10, so you need to reinstall grub2, not grub-legacy. Boot from the livecd and:

sudo -s
mount -t ext4 /dev/sda5 /mnt
grub-install --root=directory=/mnt /dev/sda

Also you can't have an sda7 without an sda6, so check your partition numbers there. Since you want to merge that space into the other partition, then you should use gparted to delete the unused partition and expand the other one to use that space first, THEN reinstall grub.