I have tried all possible grub entries and dug around web but Im still not able to boot into Vista after I installed grub.
My current menu.lst (Win Vista is on hda8-ntfs):

title Windows XP
root (hd0,0)
savedefault
makeactive
chainloader +1

title Windows Vista
rootnoverify (hd0,7)
makeactive
chainloader +1


title Ubuntu, kernel 2.6.12-9-386
root (hd0,5)
kernel /boot/vmlinuz-2.6.12-9-386 root=/dev/hda6 ro quiet splash
initrd /boot/initrd.img-2.6.12-9-386
savedefault
boot

title Debian GNU/Linux, kernel 2.6.12 Default
root (hd0,6)
kernel /boot/vmlinuz root=/dev/hda7 ro ramdisk_size=100000 lang=us apm=power-off nomce vga=791
initrd /boot/initrd.img
savedefault
boot

There are people out there who say they've accomplished it, so at least you know that it should be do-able, if not exactly how. . .

You will probably have to boot vista the same way as any Linux user with windoze on a drive partition other that hda,1. You have to remap the partitions to make vista think it's on the first partition of the first drive.

Like so:
title Windows Vista
rootnoverify (hd0,7)
map (hd0,0) (hd0,7)
map (hd0,7) (hd0,0)
makeactive
chainloader +1

or something to that effect.

This will not affect the xp setup. It will only be used when you select vista to boot.