USING A RESCUE CD to restore GRUB to MBR
I am using sysresccd aka system rescue cd from www.sysresccd.org
Rescue cds always tend to mount any partitions they discover as read only but we need them as read writeable.
eg knoppix makes my partitions available on the desktop for reading only.
Know where your /boot partition is....mine is /dev/hda1 change yours to suit.
STEP by STEP
Change bios to boot cdrom b4 hard or floppy drives
With cd in drive, boot the computer and assuming English keep pressing enter at the prompts, until you get a console or terminal prompt. If you have a non-qwerty keyboard the second prompt allows you to change the keyboard.
type mkdir /mnt/newroot
mount your real /boot partition for me its
type mount -t reiserfs /dev/hda1 /mnt/newroot
type chroot /mnt/newroot /bin/bash
# prompt will change to grub then then the cursor
type root (hd0,0)
press enter (change if /boot partition different)
type setup (hd0)
reboot and remove cd.
su = setuser to root no password is requied for knoppix or sysrescd
mkdir = make directory to anything you like but I suggest if you are reading this don't change it.
Its only a directory in your virtual = ram drive = ram disk so on reboot IT is not there.
mount means make your /boot partition readable and writeable. Yours may not be reiserfs so change reiserfs to whatever you are using.
/bin/bash is what I use, as do most newbies.
chroot means ignore all rescue cd file system, trick it into thinking your old system is back already.
grub = bootloader
root see my tutorial if you don't know how to use root
setup means let grub do its business