How to repair a corrupt MBR on linux machine?

Here are the steps:

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1. Incert CD and boot from cd(you have to change the option at BIOS).
2. boot: linux rescue //command while boot prompt comes
3. chroot /mnt/sysimage //command
4. grub-install /dev/hda //command
5. reboot the machine.
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That's it. try :)