Assuming you only have one HD, to have a clue about your partition settings do
fdisk /dev/hda
then enter 'p'
then quit
to install grub run grub
grub> root (hd0,x)
grub> setup (hd0)
grub> quit
Replace x by the number of you root partition.
You also need /boot/grub/grub.conf set to your configuration. Se if you have a grub.conf.example and try to edit it for your configuration.
This is mine:
Code:
# Boot automatically after 30 secs.
timeout 15
# By default, boot the first entry.
default 0
# Fallback to the second entry.
#fallback 1
splashimage=(hd0,2)/boot/grub/splash.xpm.gz
title Gentoo Linux
root (hd0,2)
kernel /boot/kernel-2.6.5-04.05.09 root=/dev/hda3 vga=792
# For booting WindowsXP
title WindowsXP
rootnoverify (hd0,0)
makeactive
chainloader +1