My usual habit on multi boot pc is to install each linux bootloader in its /root partition, not in the mbr, this prevents any problem when upgrading the kernel expecially having many os in the same harddrive (actually nowadays GRUD is much more efficient, but you know.....I had really bad experience with grub 2 years ago and.....)
Then I use GAG to tell the system to witch partition=bootloader move at startup

Can I do the same with VISTA boot loader?
Just have it in the VIsta active Partition?