Actually, those tips are also intended for Vista & XP. All you have to if you are planning to dual boot XP/Vista and Mac OS X is install Mac OS X first, and install Vista second, and follow steps 18-21 in that guide to get things working.
You can also first install XP/Vista, then Mac OS X, as another option and follow the same steps (if Windows NTFS "does not show up as an option in Darwin's bootloader" after installing Mac OS X).

When you boot into the Windows NTFS partition after going into Darwin, Windows bootloader will show up then, since you have XP and Vista installed (as you initially stated in your first post). You will have options there to boot into your desired Windows O/S. All should be fine.

The guide is intended for users interested in both dual, triple, quad, etc booting. =) Its only the matter in how you apply it from your perspective. =)

--Enjoy