Hi.
1) Install Vista (If you havn't already done so, if its already installed then you dont need to reinstall it)
2) Make a new partition and install Leopard. (
If you have not done this part, say and i'll explain it in more detail)
3) Make sure vista is set as the 'active partion' using fdisk.
4) Boot into vista and download and install EasyBCD.
5)

6)
If you need me to go into more detail, don't be afraid to ask
THIS GUIDE DOES NOT ALLOW DUAL BOOTING WITH XP & OSX86 ! IT ONLY WORKS IF ONE OF THE OS'S YOU WANT IS VISTA
*** UPDATE: This method does not work on CD's that automatically set OSX86 as tHe active drive, once you add the new entry you get "Chain Booting Error". Avoid using this on iAtkos v5i. I've tested it and it DOES NOT WORK!
***