Well I wonder why you would want to install Vista 32 bit and 64 bit on same machine realy?
But here are two links to help you decide:
How to dual boot Vista and XP (with Vista installed first) -- the step-by-step guide with screenshots
How to dual-boot Vista with XP (with XP installed first) - step-by-step guide with screenshots
I would learn how to dual boot Vista and XP first before attempting to triple boot.
You shoyuld check that hardware drivers are available also for all three operating systems.