I messed up my MBRs using grub2!!!

[xp_even]

I have two hard disks sda and sdb. I have Windows XP installed on sda2 and Ubuntu 10.04 on sdb5. When I installed Windows XP, Ubuntu stopped booting. I tried to repair grub2 from a Live CD unsuccessfully.

Now I have completely messed up my MBR of both HDDs. I just want to configure grub2 to load both OSes in dual boot mode.

Please help!

[devils casper]

How did you re-install GRUB?
Boot up from Ubuntu LiveCD, open Terminal and execute this

sudo mount /dev/sdb5 /mnt
sudo grub-install --root-directory=/mnt /dev/sda
sudo umount /mnt

[xp_even]

Yes. I have already tried the above commands. Now, I can't boot to either XP or Ubuntu. I am currently using the Live CD

[devils casper]

First of all, fix Windows XP boot problem. Boot up from Windows OS installation CD and select Repair. Execute fixmbr command at repair prompt. It will remove GRUB2 and rewrite Boot Section of MBR. Windows XP should boot up fine on reboot.

Did you install GRUB2 in /dev/sda or /dev/sdb?

Post the output of sudo fdisk -l command here.

[xp_even]

I think I have installed grub2 in both /dev/sda and /dev/sdb. The output of fdisk -l is as follows:

Disk /dev/sda: 160.0 GB, 160041885696 bytes
127 heads, 63 sectors/track, 39067 cylinders
Units = cylinders of 8001 * 512 = 4096512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000b747e

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1       19659    78643200    7  HPFS/NTFS
/dev/sda2           19659       39068    77643776    7  HPFS/NTFS

Disk /dev/sdb: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disk identifier: 0x000db22a

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1               2        2611    20964481    f  W95 Ext'd (LBA)
/dev/sdb2   *        2611       61355   471859200    7  HPFS/NTFS
/dev/sdb3           61355      121602   483930112    7  HPFS/NTFS
Partition 3 does not end on cylinder boundary.
/dev/sdb5               2        2008    16116736   83  Linux
/dev/sdb6            2329        2611     2268160   82  Linux swap / Solaris

[devils casper]

Have you tried to fix Windows XP? Does it boot up fine?

Try to re-install GRUB2 again. This time install it in /dev/sdb and set second Hard disk as First Boot Device in BIOS.

sudo mount /dev/sdb5 /mnt
sudo grub-install --root-directory=/mnt /dev/sdb
sudo umount /mnt

[xp_even]

Thanks a lot for the suggestions.

I did exactly as you mentioned. I can now boot into my Windows XP installation I also re-installed GRUB2 using the live CD. But after I change the boot order in the BIOS, all I get is a GRUB prompt. Did something go wrong with the GRUB install?

[devils casper]

Which OS did you install first? Windows OS or Ubuntu? Did you keep both Hard disks plugged in during installation of Ubuntu?

[xp_even]

I installed Ubuntu first, then Windows XP. Yes, both the hard disk were plugged in during the installation of Ubuntu.

[devils casper]

I installed Ubuntu first, then Windows XP.

That means, Ubuntu installer has installed GRUB in /dev/sdb only. Have you tried to swap Connectors of Hard disks in Motherboard and try to install GRUB again?