If you can chroot into the linux filesystem you can run the command
grub-install /dev/hda
http://www.redhat.com/docs/manuals/l...nstalling.html
You need a grub.conf file that's setup for your partitions and linux kernels, etc..
Here is an example grub.conf
cat /etc/grub.conf
# grub.conf generated by anaconda
#
# Note that you do not have to rerun grub after making changes to this file
# NOTICE: You have a /boot partition. This mean that
# all kernel and initrd paths are relative to /boot/, eg.
# root (hd0,2)
# kernel /vmlinuz-version ro root=/dev/hda5
# initrd /initrd-version.img
#boot=/dev/hda
timeout=10
splashimage=(hd0,2)/grub/splash.xpm.gz
default=0
title Fedora Core (2.4.26)
root (hd0,2)
kernel /vmlinuz-2.4.26 ro root=LABEL=/ rhgb idebus=66 vga=793
initrd /initrd-2.4.26.img
title Fedora Core (2.6.5-1.326custom)
root (hd0,2)
kernel /vmlinuz-2.6.5-1.326custom ro root=/dev/hda5 rhgb idebus=66 vga=793
initrd /initrd-2.6.5-1.326custom.img
title WinXP
rootnoverify (hd0,1)
chainloader +1