/*i do not know about grub,but you may use "lilo".At first,make a bootdisk for rh9.*/
#su
$fdformat /dev/fd0H1440
$uname -r
/* display kernel version */
$mkbootdisk --version version
$reboot
/*After you have installed win.Insert the bootdisk*/
#su
$vi lilo
$lilo
$reboot