Here is a guide to correctly Dual Boot Vista and XP.. Vista can be either 32 bit or 64 bit.
What you need is your Vista install disk (either Retail, System Builders or Manufacturers OEM) and your XP disk (Volume License, Retail, or System Builders.. Manufacturer OEM will not work)
You will also need to hunt down compatible XP drivers for your hardware and burn them to disk.. you will need to install these as soon as XP install is complete. After that you will need to update you XP install with the latest updates from Microsoft, and update your DirectX using the latest DirectX Redistributable (68.5MB) from March 7, 2008 (completely reinstalls DirectX to latest version and corrects any registry errors)
The guide is included at the bottom of this posting..
I do this in my computer business.. I make systems with Dual Boot capability for New and Old software compatibility.
You will not need any 3rd party applications to do this dual boot. All you need is what is listed above.
Hope that this helps.
P.S. I can't believe with all the intelligent people on the web.. only 5 people I have found (including myself) figured this out.. it is very simple .. longest part is partitioning the HDD.. however if you have 2 drives.. makes it much easier.
Just remember, when dual booting, you must install software to each OS independently.. you can not cross partitions / drives for software.. each OS uses independent registry settings.
Also, tweaks for going over the 3 GB limit in XP will not work on Dual Boot since the OS uses Vista's boot loader (reference the /3GB boot.ini switch.. XP will not have a boot.ini file nor will it recognize one if you add it to the OS)
anyhow.. hope that this helps.
Edited by Pestalence_XC - 5/31/08 at 9:25pm