This is how I boot Windows XP via Grub which was installed by the Kubuntu 6.10 CD
Added this entry to the end of the file /boot/grub/menu.lst :
title Microsoft Windows
map (hd0) (hd1)
map (hd1) (hd0)
I'm told the map commands make Windows think it's the first hard drive (hd0). There are several variations of this command if this doesn't work for you.
You'll want to replace the bold values with your own settings which you should be able to see via "fdisk -l".
hd0 = first hard drive
hd1 = second hard drive
hd1,0 = second hard drive , first partition