if you have any kind of linux livecd you can fix the problem manualy:
1. install win
2. boot from livecd
3. mount your root partition, proc partition and boot partition in place of mounted root partition, then simply say 'chroot <place_where_you_mounted_root>'
4. use your favourite console editor (vi, nano, etc...) to edit grub.conf (menu.lst) in /boot/grub (or in place your boot partition generaly mounted) and add there two sections for windows:
and for linux:
kernel (hd0,1)/<kernel_name-version> root=/dev/hda6
5. enter command:
# grub-install /dev/hda
(hd0,0) means /dev/hda1, (hd0,1) - /dev/hda2, also (hd1,0) and (hd1,1) mean /dev/hdb1 and hdb2 accordingly. so you should choise right names for (hdx,y) and /dev/hd. if in doubt - you can use fdisk (or cfdisk) to see partition table (and mount them).
if all done right, then two new entries ('linux' and 'windows') should appear in grub menu.