Oops, misunderstood that. First look at /boot/grub/menu.lst and see if it looks ok and contains lines looking something like this at the bottom:
<snip>
title Windows 2000
rootnoverify (hd0,0)
makeactive
chainloader +1

title Debian GNU/Linux, kernel 2.6.14.2-191105
root (hd1,0)
kernel /boot/vmlinuz-2.6.14.2-191105 root=/dev/hdb1 ro ramdisk_size=100000 \
lang=us hda=scsi hdb=scsi nomce vga=794 splash=silent
initrd /boot/initrd.splash
savedefault
boot
<snip>

Then install grub to the mbr. This assumes your box boots from hda first so change hda to your boot disk (sda?):
- boot cd
- sudo mount /mnt/hdd2
- sudo grub-install --recheck --no-floppy --root-directory=/mnt/hdd2 /dev/hda