if linux automounts the windows hard drive, run
whilst at the console, that will give you the actual mount point
So, if you find the actual HDD then you can edit the grub boot menu
/boot/grub/some file ... real obvious when you look, but i haven't got it here :P
alternatively, /etc/fstab contains a list of all mount points
IF however you don't have a mount point configured, then you need to work out where the HDD is actually connected
primary master is /dev/hda
primary slave is /dev/hdb
seconday master is /dev/hdc
and secondary slave is /dev/hdd
so where ever it is. then you need to know what partition on it, but that's easy enough really coz odds are it's the first one
so just try mounting the different /dev/hdb1 etc to some directory (that's empty)
for instance mkdir ~/temp
mount /dev/hdb1 ~/temp
~ is your home directory /home/YOU
when you find what HDD contains all the windows directories, just point grub to it.
Now be reasonable run df first, to see if it's mounted,
then mount the drives in sequence so mount the first, then umount it, then the second until you're done
you might need to be root, i forget, you will need to be root to edit the grub menu.
Unfortunately all of this happens in the console, except for editing grub.
One last thing, don't change the lines in grub that relate to linux, coz if you do, you might break the bootloader (so if you ain't sure, BACK UP)
best of luck